SPM Biology Form 4 KSSM 9789672250838

Biology Form 4 Integrated Curriculum For Secondary Schools Kurikulum Standard Sekolah Menengah (KSSM) for 2020 and onwar

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SPM Biology Form 4 KSSM
 9789672250838

Table of contents :
01 DLP_BioT4(FP)-Prelim(OF)_8PP
01Theme_1_3p (13Nov)
02 BioT4(NC)-B1-FA_EN 6pp
03 BioT4(NC)-B2-FA_EN 6pp
05 BioT4(NC)-B4-FA_EN 6pp
06 BioT4(NC)-B5-FA_EN 6pp
10 BioT4(NC)-B8-FA_EN 6pp
11 BioT4(NC)-B9-FA_EN 6pp
12 BioT4(NC)-B10A-FA_EN 6pp
13 BioT4(NC)-B10B-FA_EN 6pp
14 BioT4(NC)-B11-FA_EN 6pp
15 BioT4(NC)-B12-FA_EN 6pp
16 DLP_Biology_F4 (Loo)_13_7PP
18 DLP_Biology_F4_15_(Loo)_9PP
19 DLP_BioF4_Postlims_4PP
Errata_BioF4(DLP)_12_6_20

Citation preview

KURIKULUM STANDARD SEKOLAH MENENGAH FORM

BIOLOGY 4 WRITERS Gan Wan Yeat Nor Azlina binti Abd. Aziz Yusmin binti Mohd. Yusuf Noor Haniyatie binti Ibrahim

TRANSLATORS Michelle Harris Nor Azlina binti Abd. Aziz Yusmin binti Mohd. Yusuf

EDITORS Stella Melkion Mohd Haziq bin Kahar

DESIGNER Siti Aishah binti Mohd

ILLUSTRATORS Hazli bin Hashim Sara Fateha binti Muhd Kamil Nigel Teoh Tsen Wee Ling Chan Khong Wei Lin Pu Kuan

2019

KEMENTERIAN PENDIDIKAN MALAYSIA Book Serial No.: 0177 KPM2019 ISBN 978-967-2250-83-8 First Published 2019 © Ministry of Education Malaysia All rights reserved. No part of this book may be reproduced, stored in any retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without prior permission of the Director General of Education, Ministry of Education Malaysia. Negotiation is subject to the calculation of royalty or honororium. Published for the Ministry of Education Malaysia by: Must Read Sdn. Bhd., No. 33 Jalan SBC 6 Taman Sri Batu Caves 68100 Batu Caves Selangor Darul Ehsan No. Tel: 03 – 6187 1611 Fax: 03 – 6187 1613

Acknowledgement The publishing of this textbook involves cooperation from various parties. Our wholehearted appreciation and gratitude goes out to all involved parties: • Educational Resources and Technology division. • Committee members of Penyemakan Naskhah Sedia Kamera, Educational Resources and Technology Division, Ministry of Education Malaysia. • Committee members of Penyemakan Pembetulan Naskhah Sedia Kamera, Educational Resources and Technology Division, Ministry of Education Malaysia. • Officers of the Educational Resources and Technology Division and the Curriculum Development Division, Ministry of Education Malaysia

Design and typesetting by: Angevil Design & Marketing

• Officers of the English Language Teaching Centre (ELTC), Institute of Teacher Education Malaysia, Ministry of Education Malaysia.

Font style: Minion Pro Font size: 11 pt.

• Chairperson and members of the Quality Control Panel.

Printed by: Aslita Sdn. Bhd., No. 10 & 12, Jalan 2/10B, Spring Crest Industrial Park, 68100 Batu Caves, Kuala Lumpur

• Editorial Team and Production Team, especially the illustrators and designers.

Preface This textbook has been written based on the Dokumen Standard Kurikulum dan Pentaksiran (DSKP) for Biology Form 4, published by the Ministry of Education, Malaysia. It is guided by the concepts of Scientific Skills, Science Process Skills, Higher Order Thinking Skills, 21st Century Skills and the STEM teaching and learning approach. The objective of this textbook is to develop well-rounded pupils and to equip them with the skills needed for the 21st century.

Special features of this book: Biological Lense Additional information related to theories and concepts

Our World of Biology

Higher-order thinking questions which cover applying, analysing, evaluating and creating questions

Illustrates the application of theories and concepts learnt in everyday life

Brainstorm! Challenges pupils to think critically and creatively

Malaysian Innovation The successes of Malaysian scientists and the related scientific and technological developments in Malaysia

Kerjaya Milenia Millennial Career

Take Note! Reminders for students when carrying out activities or experiments

Questions to test pupils’ understanding at the end of every subtopic

Summative Practice Questions to test pupils’ understanding at the end of every chapter

Describes careers related to a concept or topic

Summary A summary of the main concepts

STEM Bulletin Highlights current developments in the related fields of science and technology

Self Reflection A checklist on the mastery of concepts for pupils’ reference

Across the Fields Shows the connection between biology and other fields

Activity Zone

4.2.3

Learning Standard based on the Form 4 Biology Dokumen Standard Kurikulum dan Pentaksiran (DSKP)

Suggested activities for pupils to carry out

iii

A Fun Learning Experience This book consists of digital resources in the form of Augmented Reality (AR) and QR codes. These resources can be accessed by scanning the AR or QR codes which can be found in selected pages, using a smartphone or electronic tablet.

Exciting New Experience While Reading

Exciting New Experience While Reading Exciting New Exp

Steps in accessing the AR resources

1

2

1

2

2

Scan

Scan

Exciting New Experience While Reading 1

2

Scan

SnapLearn

SnapLearn

Download Snaplearn APP

Activate by scanning this QR Code

3

1 3

3 AR

3

SnapLearn Scan to experience AR

SnapLearn Download Download the Snaplearn APP iOS 7.0 or Android 4.0 and above

SnapLearn app onto your electronic device.

Download naplearn APP

2

Scan the pages with the above icon Download Scan to to access the AR resources. APPAR Snaplearn experience

Activate by scanning this QR Code Click on the button and scan the above code.

Activate by scanning this QR Code Accessing the QR resources iOS 7.0 or Android 4.0 and above

Scan to experience A iOS 7.0 o

A variety of complementary content such as videos, additional activities, quizzes and additional information can be accessed by scanning the QR codes found in selected pages using any QR code scanner.

iOS 7.0 or Android 4.0 and above

iv

Activa th

ICT 4.4

ICT 7.1

ICT 10.1

Quiz: Test your understanding of lipids

Video: Aerobic respiration

Activity: Studying the effects of changes in total surface area to volume ratio (TSA/V) on diffusion rate.

Contents



Title Page

i

Copyright Page and Acknowledgments ii Preface iii

1

FUNDAMENTALS

BIOLOGY

OF

1 Introduction to Biology and Laboratory Rules

1 2

5 Metabolism and Enzymes

84

5.1 Metabolism 5.2 Enzymes 5.3 Application of Enzymes in Daily Life

86 86 95

6 Cell Division

98

6.1 Cell Division 6.2 Cell Cycle and Mitosis 6.3 Meiosis 6.4 Issues of Cell Division on Human Health

100 101 105

108 1.1 Fields and Careers in Biology 4 1.2 Safety and Rules in a Biology Laboratory 6 7 Cellular Respiration 112 1.3 Communicating in Biology 11 7.1 Energy Production through 1.4 Scientific Investigation in Biology 15 Cellular Respiration 114 7.2 Aerobic Respiration 115 2 Cell Biology and Organisation 20 7.3 Fermentation 117 2.1 Cell Structure and Function 22 2.2 Living Processes in Unicellular Organisms 28 2.3 Living Processes in Multicellular Organisms 30 2.4 Levels of Organisation in Multicellular 125 Organisms 37 8 Respiratory Systems in

2

3 Movement of Substances across a Plasma Membrane

3.1 Structure of Plasma Membrane 3.2 Concept of Movement of Substances across a Plasma Membrane 3.3 Movement of Substances across a Plasma Membrane in Living Organisms 3.4 Movement of Substances across a Plasma Membrane and its Application in Daily Life

44 46 49 57

65

4 Chemical Compositions in a Cell

70



72 73 76 77 79

4.1 Water 4.2 Carbohydrates 4.3 Proteins 4.4 Lipids 4.5 Nucleic Acids

PHYSIOLOGY OF HUMANS AND ANIMALS Humans and Animals

8.1 8.2 8.3 8.4

Types of Respiratory System Mechanisms of Breathing Gaseous Exchange in Humans Health Issues Related to the Human Respiratory System

9 Nutrition and the Human Digestive System

9.1 Digestive System 9.2 Digestion 9.3 Absorption 9.4 Assimilation 9.5 Defaecation 9.6 Balanced Diet 9.7 Health Issues Related to the Digestive System and Eating Habits

126 128 132 136

138

142 144 144 151 153 155 156 161

v





10 Transport in Humans and Animals 10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8

Types of Circulatory System Circulatory System of Humans Mechanism of Heartbeat Mechanism of Blood Clotting Blood Groups of Humans Health Issues Related to the Human Circulatory System Lymphatic System of Humans Health Issues Related to the Human Lymphatic System

11 Immunity in Humans

11.1 11.2 11.3 11.4

166 168 173 180 183 185 187 189 193

198

Body Defence 200 Actions of Antibodies 204 Types of Immunity 205 Health Issues Related to Immunity 209

12 Coordination and Response in Humans 214 12.1 Coordination and Response 216 12.2 Nervous System 220 12.3 Neurones and Synapse 223 12.4 Voluntary and Involuntary Actions 226 12.5 Health Issues Related to the Nervous System 230 12.6 The Endocrine System 233 12.7 Health Issues Related to the Endocrine System 238

vi

13 Homeostasis and the Human Urinary System 244 13.1 Homeostasis 13.2 The Urinary System 13.3 Health Issues Related to the Urinary System

246 252 259



14 Support and Movement in Humans and Animals 14.1 14.2 14.3 14.4

Types of Skeleton Musculoskeletal System of Humans Movement and Locomotion Health Issues Related to the Human Musculoskeletal System

15 Sexual Reproduction, Development and Growth in Humans and Animals

264 266 267 272 277

284

15.1 Reproductive System of Humans 286 15.2 Gametogenesis in Humans 288 15.3 Menstrual Cycle 293 15.4 Development of Human Foetus 297 15.5 Formation of Twins 300 15.6 Health Issues Related to the Human Reproductive System 302 15.7 Growth in Humans and Animals 303

Glossary 311 References

314

1

THEME

FUNDAMENTALS OF BIOLOGY

This theme aims to provide a basic understanding of biology through scientific investigation with the inquiry approach. This theme focuses on cells as basic living units, the role of the plasma membrane in cell physiology, chemical composition in cells and cell division.

Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7

Introduction to Biology and Laboratory Rules Cell Biology and Organisation Movement of Substances across a Plasma Membrane Chemical Composition in a Cell Metabolism and Enzymes Cell Division Cellular Respiration

1

CHAPTER

Introduction to Biology and Laboratory Rules

Do You KNOW…

What are the effects of the Industrial Revolution 4.0 on the fields of biology?

• What does bio logy mean? • What are the fie lds of study in biolog y? • What type of ca reers can you purs ue in the fields of biolog y? • What are the sa fety equipment and rules in a biology laborat ory? • How do you co mmunicate in the fie lds of biology? • How is knowled ge gained through scientific investigat ion?

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1.1 Fields and Careers in Biology 1.1.1 State the meaning of biology. 1.1.2 List the fields of study in biology, careers and development in related fields. 1.1.3 Generate ideas about development in biology fields and contribution of technology in biology to humans. 1.1.4 Give examples of careers related to the fields of biology. 1.2 Safety and Rules in Biology Laboratory 1.2.1 Explain self protective equipment and their functions. 1.2.2 Identify and justify substances that can be disposed into the sink. 1.2.3 Identify and justify substances that cannot be disposed into the sink. 1.2.4 Describe methods in managing biological wastes. 1.2.5 Communicate about steps to manage accidents in a laboratory. 1.2.6 Conclude safety practices in a biology laboratory. 1.3 Communicating in Biology 1.3.1 Communicate by constructing tables based on experimental data. 1.3.2 Plot a suitable graph based on the data from an experiment. 1.3.3 Sketch biological drawings based on observations. 1.3.4 Identify body planes, sections and directional terms in organisms. 1.4 Scientific Investigation in Biology 1.4.1 Design an experiment to solve a problem using scientific investigation methods.

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1.1

Fields and Careers in Biology What is Biology? The word ‘Biology’ comes from the Greek word, ‘bios’ meaning life, and ‘logos’ meaning study. Biology is a detailed study of living things in the natural environment. Biology allows us to understand the structure and function of organisms, as well as the relationships and interactions between organisms with their environment. Some examples of biological study areas are shown below in Photograph 1.1.

ICT 1.1 Video: What is Biology? (Accessed on 21 August 2019)

Botany Study of plant life Physiology Study of the function and mechanisms in organisms Ecology Study of the interactions between organisms and their environment

Genetics Study of inheritance and genetic variation

Microbiology Study of microorganisms PHOTOGRAPH 1.1 Examples of biological research areas

Biological Lens The three-dimensional (3D) bioprinting technique is used to print and form artificial tissues and assist in the field of modern medical engineering.

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Malaysian Innovation One of Malaysia’s success in technological innovation is the production of biological scaffold derived from shellfish for use in dental treatment. Technological innovation in Malaysia is spearheaded by researchers from public and private universities and research institutions. 1.1.1

1.1.2

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Biological knowledge has contributed a lot to mankind. Here are some examples of how biology has contributed to everyday life (Photograph 1.2). MEDICAL

CHAPTER 1

The contribution of biology in everyday life

PHARMACEUTICAL

In vitro fertilisation, family planning, plastic surgery and gene therapy.

FOOD PRODUCTION Use of microorganisms in the production of cheese, soy sauce, tapai and tempe.

Production of synthetic vitamins, vaccines, insulin and synthetic enzymes.

AGRICULTURE Transgenic crops and animals, hydroponic and aeroponic technology.

PHOTOGRAPH 1.2 Contribution of biology in everyday life

Careers in Biology I am using information technology to produce medicines. What is my profession?

I want to be a wildlife biologist. Which biological field should I choose?

PHOTOGRAPH 1.3 Careers in biology

Formative Practice

1.1

1 What does biology mean? 2 List three fields of biology and the development in those fields.

3 Choose one development in the field of biology and discuss its contributions to humans. 4 Name five careers that are related to the fields of biology.

1.1.3

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1.2

Safety and Rules in Biology Laboratory A biology laboratory is essential for conducting scientific investigations. To avoid unwanted incidences, we must always adhere to the safety rules and measures in a biology laboratory. We must also know the personal protective equipment and understand their functions.

EMERGENCY SHOWER STATION Used when chemicals or hazardous substances come into contact with the skin.

FUME HOOD To avoid breathing in hazardous gases like chlorine, bromine and nitrogen dioxide.

EYE WASH STATION Used to wash the eyes when exposed to chemicals or hazardous substances.

LAMINAR FLOW CABINET Provides a flow of filtered air for a clean work area in the laminar flow cabinet.

BIOLOGICAL SAFETY CABINET Provides an enclosed work space to study materials that have been (or are likely to have been) contaminated by pathogens.

PHOTOGRAPH 1.4 Equipment and their functions in a biology laboratory

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CHAPTER 1

GOGGLES To protect the eyes from hazardous chemicals

FACE MASK To protect against smoke, vapour and dust that can affect the respiratory system

LABORATORY GLOVES To handle biological samples

HANDWASH To remove germs on hands

LAB COAT To protect the skin and clothes from dangerous chemical splashes

Brainstorm!

Substances that can be disposed into the sink

Why can certain substances be disposed into the sink?



Chemicals with pH values 5–9



Low concentration liquids and solutions that are harmless to users (sucrose solution, dye solution, distilled water)

Substances that cannot be disposed into the sink • Organic solvents (acetone, alcohol, benzene)

LAB SHOES To prevent injury from glass shards and chemical spills



Substances that have a pH value of less than 5 or more than 9



Chemicals (acids, greases, oils)



Solid waste (chemicals, glass, rubber)



Heavy metals (mercury)



Volatile substances



Toxic substances



Organic waste (microorganisms, carcases)



Reactive substances



Radioactive substances

Brainstorm! Why can’t certain substances be disposed into the sink?

PHOTOGRAPH 1.5 Personal protective equipment and their functions in the biology laboratory 1.2.1

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1.2.2

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Methods for managing biological waste After carrying out an experiment, there are wastes that need to be managed with care before disposal. Methods for managing different biological wastes according to Standard Operating Procedures are listed in Table 1.1. TABLE 1.1 Methods for managing biological waste (Photograph 1.6)

Biological waste categories

Example

Management method

Category A (sharp wastes)

Sharp instruments such as syringes, needles, glass, scalpel and other sharp instruments that can cause injuries

Placed into a special bin for sharp material disposal. This bin does not need to be sterilised.

Category B (non-sharp wastes)

Biological solid waste such as gloves, tissue papers, petri dishes, plastic culture containers and hardened agar

Packed first in autoclave resistant biohazard plastic bags, sterilised in an autoclave for decontamination, and then placed into a biohazard bin (Photograph 1.6). Biohazard plastic bags cannot be thrown into regular waste baskets.

Category C (animal carcases)

Animal carcases, organs and tissues

Wrapped carefully in absorbent material (such as tissue papers), packed carefully into a biohazard plastic bag and frozen.

Category D (liquids)

Broth culture and liquid medium such as blood

All biological liquid waste must be decontaminated by autoclaving before disposal. Sterilised biological liquid wastes must be disposed immediately.

Take Note! •



Biohazard plastic bag

Decontamination by autoclaving is done at a temperature of 121°C and pressurised at 15 psi for 20 minutes. Biohazard plastic bags that have been sterilised in an autoclave and sharp waste bin must be stored temporarily in a controlled storage place until the scheduled time for disposal.

Sharp waste bin

Autoclave Biohazard bin

PHOTOGRAPH 1.6 Equipment to manage biological wastes

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CHAPTER 1

Accidents in the laboratory Accidents in laboratories can be caused by carelessness, negligence or lack of skill in carrying out experiments. Here are the steps in managing accidents in laboratories. STEPS TO HANDLE GENERAL CHEMICAL SPILLS 1. Inform your teacher. 2. Declare the spill area as a restricted zone. 3. Prevent the chemical spill from spreading using sand. 4. Scoop up the chemical spill using appropriate equipment. 5. Dispose it safely.

STEPS TO HANDLE MERCURY SPILLS 1. Inform your teacher. 2. Declare the spill area as a restricted zone.

PHOTOGRAPH 1.7 Chemical spills are stopped from spreading by using sand

3. Sprinkle sulphur to cover the mercury spills. 4. Call the fire and rescue department.

Practices in a biology laboratory

Activity Zone

The biology laboratory is a place for learning and research. However, there are some general safety rules that must always be practised by pupils.

CLOTHING ETHICS Use a lab coat, gloves, safety shoes and goggles when appropriate.

Find information on handling accidents in laboratories set by the following agencies: (i) Malaysian Biosafety and Biosecurity Association (MBBA). (ii) National Institute of Occupational Safety and Health (NIOSH).

LABORATORY SAFETY RULES •

Do not work alone in the laboratory without supervision.



Wash your hands after conducting an experiment.



SAFETY MEASURES FOR FIRES •

Do not bring in irrelevant items into the laboratory.

Stop work immediately and switch off all nearby power sources. Unplug appliances.





Clean your workstation using disinfectant.

Exit the laboratory according to the emergency exit plan.



Dispose wastes according to the set procedures.



Call the fire and rescue department.



Do not panic and stay calm.



Do not turn back to collect your belongings.



Assemble at the assembly point.



Do not eat and drink in the laboratory.



Identify all safety symbols on substances and equipment before use.

1.2.5

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HANDLING GLASS AND CHEMICALS

HANDLING LIVE SPECIMENS



Be cautious when handling hot glassware.





Report any damaged equipment or glassware to teachers immediately.

Use appropriate gloves when handling biological specimens.





Keep flammable chemicals away from fire sources.

Specimens that are not harmful and have been dissected should be buried or frozen.





Do not touch, taste and smell chemicals directly.

Wash hands with antiseptic detergents before and after experiments.



All surfaces and workstations should be cleaned with disinfectant before leaving the lab.

EMERGENCY HELP The following procedures should be followed in the event of an accident: •

Inform your teacher.



Call the fire and rescue emergency number.



Remove the victim from the scene.



Give emergency treatment.



Make the place of accident as a restricted area.

Scientific Attitudes and Noble Values Scientific attitudes and noble value practices when carrying out a scientific investigation:







Having interest and curiosity towards the environment. Being honest and accurate in recording and validating data. Being diligent and persevering in carrying out a study.

• •

Formative Practice

2 After conducting an experiment, you are given a task to manage the disposal of Category B biological waste (non-sharp wastes). Think of the best way so that the biological waste does not affect the environment.

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1.2

1 State three examples of personal protective equipment in the lab and their functions.

10



Being responsible about the safety of oneself, others and the environment. Appreciating and practising clean and healthy living. Appreciate the contributions of science and technology. Think critically and analytically.

3 An accident has occurred in the laboratory involving mercury spills. Explain the steps in handling the mercury spills. 4 Chemicals must be handled with care to avoid unwanted accidents. List steps for proper handling of chemicals.

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Biologists who conduct research need to communicate their research findings. Communication in biology involves tables, graphs and biological drawings.

CHAPTER 1

1.3

Communicating in Biology Tables

Tables are used to record and present data. When you conduct an investigation, the experimental data needs to be recorded in a suitable table. A table allows you to organise data systematically for easy comparison. The headings in the table consist of the manipulated variable and the responding variable with the respective unit. ICT 1.2 a. The manipulated variable is placed in the column on the Video: How to left side. draw a graph (Accessed on 21 b. The responding variable is placed in the column on the August 2019) right side. Table 1.2 shows an example of a table in an experiment on the TABLE 1.2 Volume of oxygen released by effects of different temperatures (manipulated variable) aquatic plants at different temperatures on the volume of oxygen (O2) released by aquatic plants (responding variable). Temperature Volume of oxygen (°C)

released (cm3)

30

2.0

40

14.0

50

12.0

60

6.0

70

3.0

Graph The relationship between the manipulated variable and responding variable can be illustrated in the form of a graph. There are several types of graphs such as line graphs, bar charts and histograms. The line graph shown in Figure 1.1 is based on the data in Table 1.2. GENERAL METHOD OF DRAWING A GRAPH

Volume of oxygen released (cm3)

Volume of oxygen released versus temperature

Temperature (°C)



The responding variable is represented by the vertical axis (y-axis) and the manipulated variable is represented by the horizontal axis (x-axis).



The scaling on the axis must be uniform.



Mark the points with an appropriate symbol such as ‘x’.



Title the graph: “Graph (responding variable) versus (manipulated variable)”.

FIGURE 1.1 Example of a line graph 1.3.1

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Number of Form 4 pupils versus blood type

A bar chart presents data using vertical bars that are not attached to each other.

Number of Form 4 pupils

METHOD OF DRAWING A BAR CHART



Draw two axes, the horizontal axis/X to represent the manipulated variable and the vertical axis/Y to represent the responding variable.



Each width of the bar needs to be uniform.



The bar height depends on the frequency of the data.



Bar charts are used to make comparisons between two or more items at a time.

Blood type FIGURE 1.2 Example of a bar chart

Take Note! The graph title must be written as “ versus ”.

Number students versus height Number of of pupils versus height

Height (cm)

161 - 165

156 - 160

151 - 155

0 146 - 150

The size or width of the bars must be the same for all class gap with no spacing between the bars.

141 - 145

Insert labels and units on the axes.



2

136 - 140



4

131 - 135

Draw two axes where the horizontal axis/X represents the data that has been divided into groups according to the appropriate range while the vertical axis/Y shows the frequency.

126 - 130



6

121 -125

METHOD OF DRAWING A HISTOGRAM

8

115 - 120

A histogram shows the visual distribution of data and the frequency of a value in a data set.

Number of students Number of pupils

10

Height (cm)

Biological drawings

FIGURE 1.3 Example of a histogram

Biological drawings must be exact to give an accurate representation of an observed specimen.

Characteristics of biological drawings • Large and accurate; use a sharp pencil and not a colour pencil or pen. • Not shaded artistically. • Lines drawn must be clear, clean and continuous. Do not use a ruler to draw the outline of a specimen. 12

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Therefore, the magnification factor is 2x.

CHAPTER 1

• Drawings must be labelled. Label lines must point to the correct structure, no arrowheads, must be straight and not cross each other. • Drawings must have titles. • Each structure in the drawing must be placed in the correct position, and its size should be proportionate to the rest of the structures. • A plan drawing is a line drawing that shows the outline of a structure. • A detailed drawing shows the cells in a structure. • The magnification factor of a drawing must be stated, for example: Length of drawing in cm 2.4 = = 2x Length of specimen in cm 1.2 phloem pith

cortex

xylem

phloem pith xylem

(b) Detailed drawing

horizontal plane (a) Plan drawing

frontal plane

FIGURE 1.4 Example of (a) plan drawing and (b) detailed drawing of cross section of dicotyledon stem

Plane, section and direction In biology, research and observation of an organism’s structure are done based on the plane, section and direction. The plane refers to a flat surface of shadow passing through the body. There are three main planes used (Figure 1.5): • sagittal plane (divides the body into right and left parts) • frontal plane (divides the body into frontal and rear parts) • horizontal plane (divides the body into upper and lower parts)

sagittal plane

FIGURE 1.5 Sagittal, frontal and horizontal planes 1.3.4

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Cross section divides the structure into upper and lower portions horizontally while longitudinal section divides the structure into left and right portions (Photograph 1.8).

Longitudinal section Cross section

PHOTOGRAPH 1.8 Longitudinal section and cross section of a red carrot

Many anatomical drawings of animals and plants need to be labelled with direction. All vertebrates have the same fundamental body plan that is symmetrical. Direction consists of anterior, ventral, posterior, dorsal, superior, inferior and lateral. By studying anatomical directions in biology, you can identify the orientation of the vertebrate that is stated. superior

Towards the lower part of the body

SUPERIOR The part that is above all other parts or towards the head LATERAL

DORSAL

VENTRAL

Towards the upper part of the body

dorsal lateral

Far from the midline or at the side of the body

posterior anterior

INFERIOR Situated below other parts or towards the feet

ventral

ANTERIOR Towards the front of the body

POSTERIOR Towards the back part of the body

inferior FIGURE 1.6 Directional terms in biology

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CHAPTER 1

1.4

Scientific Investigation in Biology Scientific investigations prove the validity of a hypothesis that has been made. The following are the steps in carrying out a scientific investigation.

1

Identifying problems that can be tested using a scientific investigation

2 Forming a hypothesis

3 Identifying and controlling variables and data collection method 4 Planning and carrying out a scientific investigation

5 Collecting data 6 Interpreting data and

results through scientific reasoning

7 Forming a conclusion 8 Writing a report

After you have completed the experiment, you need to write a report to prove that you have conducted the experiment. If a report is not written, your experiment will be invalid. Here is an example of an experimental report framework.

Activity itcA 1s.2eitiv1.1

Studying the effects of an activity on a pupil’s pulse rate

Experiment

Problem statement What is the effect of a vigorous activity on the pupil’s pulse rate?

Hypothesis The pupil’s pulse rate increases after a vigorous activity.

Variables Manipulated: Vigorous activity Responding: Pupil’s pulse rate Fixed: Pupil

Materials and apparatus Stopwatch

Specimen

Measuring pulse rate

Pupil

Procedure 1 Count the pupil’s pulse for one minute before carrying out the activity. 2 The pulse is counted by placing two fingers on the wrist. 3 The pupil is asked to carry out a vigorous activity for three minutes. 4 After the vigorous activity is carried out, count the pupil’s pulse again for one minute. 5 Record the results in the following table. 1.4.1

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Results Pulse rate (number of pulse beats per minute) Pupil

Before the vigorous activity

After the vigorous activity

A

Take Note! Make sure the pupil is seated quietly when the pulse rate is taken.

B

Discussion 1 State the relationship between the pupil’s pulse rate with vigorous activity. 2 Explain why the pulse rate increases after doing a vigorous activity.

Conclusion Based on the results, state if the hypothesis can be accepted or rejected.

Report Prepare a complete report based on the experiment that was carried out.

Formative Practice

Take Note! Make sure pupils with health issues such as breathing and cardiovascular problems do not take part in this activity.

1.3

1 The table below shows the results of an experiment to study the effects of substrate concentration on biochemical reactions.

Test tube

Starch concentration (%)

Time to complete starch hydrolysis (minute)

Rate of hydrolysis of starch (% minute-1)

A

1.0

2.5

0.4

B

2.0

3.0

0.7

C

3.0

3.5

0.9

D

4.0

4.0

1.0

(a) Based on the table above, identify the manipulated variable and responding variable. (b) Draw a graph of rate of starch hydrolysis versus starch concentration using the correct scale and units. 2 State five characteristics that a biological drawing must have. 3 State the three main planes that are used for observation of the structure of an organism. 4 List the steps in a scientific investigation.

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CHAPTER 1

Summary INTRODUCTION TO BIOLOGY AND LABORATORY RULES

Fields and Careers in Biology

Safety and Rules in the Biology Laboratory

• Meaning of biology • Developments in biology • Contribution of biology in life • Careers in biology

• Personal protective equipment and their functions • Methods of managing biological wastes • Safety practices in the biology laboratory

Communicating in Biology

• Tables • Graphs • Bar charts • Histograms • Biological drawings • Planes, sections and directions

Scientific Investigation in Biology Steps in a scientific investigation

Self Reflection Have you mastered the following concepts? • Meaning of biology • Areas of study in biology, careers and progress in the related fields • Development in the fields of biology and contribution of biological technology to humans • Careers related to biology • Personal protective equipment and their functions • Substances that can be disposed into the sink • Substances that cannot be disposed into the sink • Methods of managing biological waste • Steps to manage accidents in the laboratory • Practices in a biology laboratory • Tables based on data from experiments conducted • Appropriate graphs based on data from experiments conducted • Biological drawings based on obser vations made • Body planes, sections and directional terminology in organisms • Experiment to solve problems using the scientific investigation method

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Summative Practice 1 1 Why are you not allowed to wear slippers while in the laboratory? 2 Give the meaning of (a) cross section (b) longitudinal section 3 Discuss methods of biological waste management. 4 Describe the stages involved in a scientific investigation. 5 (a) An experiment was conducted to demonstrate the hydrolysis of starch by the amylase enzyme. Experiment apparatus provided are as in Figure 1. After an hour, samples from each test tube were tested using iodine test.

thermometer

110



A

B

40

50

60

70

80

90

100



-10

0

10

20

30

water bath (37ºC)

1 ml starch solution + 1 ml 0.1% amylase

1 ml starch solution + 1 ml distilled water

FIGURE 1

(b)

(i) Identify the problem statement for this experiment. (ii) State the appropriate hypothesis for this experiment. (iii) Identify the manipulated variable, responding variable and constant variable. A pupil spilled hydrochloric acid while conducting an experiment. What action should be taken by the pupil?

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CHAPTER 1

Essay Questions 6

FIGURE 2

(a) Figure 2 shows an accident in a biology laboratory due to two pupils playing with fire while conducting an experiment. The accident caused one of the boys’ shirt to catch fire. Explain what the victim's friend should do. (b) Azlin is conducting an experiment involving the use of a thermometer. Accidentally, she drops the thermometer on the floor and the thermometer breaks. What steps does Azlin need to take in handling the spilled mercury waste? Explain your answer. (c) Plan an experiment to study the effect of sugar on the growth of yeast. Enrichment 7 The emergence of Industrial Revolution 4.0 has begun to change the way we work and the way we live. Various industries are experiencing drastic changes and at the same time transforming jobs related to those industries. In your opinion, what is the effect of the Industrial Revolution 4.0 to everyday life? Justify your opinion. 8 If you are given an assignment by your teacher to collect information on the development of tissue culture technique in Malaysia, suggest the steps that need to be taken to complete your assignment. Complete answers are available by scanning the QR code provided

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2

CHAPTER

Cell Biology and Organisation



Which cell has the longest life span?

Do you KNOW...

What are the compo nents of plant cells and anim al cells? • What is the life process of the unicellular organism ? • What is the relat ionship between specialise d cell structures and their functions? • What are the lev els of organisation in mult icellular organisms?

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2.1 Cell Structure and Function 2.1.1 Prepare microscope slides of animal and plant cells. 2.1.2 Identify the structures of animal and plant cells based on observations through a light microscope. 2.1.3 Analyse the components of animal and plant cells as seen on micrographs. 2.1.4 State the main functions of components of animal and plant cells as seen on micrographs. 2.1.5 Compare and contrast components of animal and plant cells. 2.2 Living Processes in Unicellular Organisms 2.2.1 Conceptualise living processes in unicellular organisms such as Amoeba sp. and Paramecium sp. 2.2.2 Deduce living processes in unicellular organisms as seen through a light microscope. 2.3 Living Processes in Multicellular Organisms 2.3.1 Correlate the uniqueness of specialised cell structures with their functions in multicellular organisms. 2.3.2 Identify specialised cells in multicellular organisms. 2.3.3 Analyse the density of certain organelles with the functions of specialised cells in multicellular organisms. 2.3.4 Describe the effects of deficiency, absence or failure in the function of an organelle of certain cells in multicellular organisms. 2.4 Levels of Organisation in Multicellular Organisms 2.4.1 Make a sequence of levels of organisation in multicellular organisms. 2.4.2 Identify cells, tissues or organs in an organ system. 2.4.3 Communicate about organ systems in multicellular organisms with their main functions.

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2.1 Activity vitcA 1.2seiti2.1

Cell Structure and Function You may still recall the shape of cells you learned in Form 1. Much like the bee hive which is made up of hexagonal-shaped units, all living things are also made up of cells that are combined together. Cells are the basic units of all living things. Let us examine the structure of animal cells and plant cells through a light microscope.

Preparing and examining slides of plant cells

Observation

Materials One big onion, iodine solution, distilled water and filter paper

Apparatus Glass slides, cover slips, light microscope, scalpel, a pair of forceps, dropper and mounting needle

Procedure 1 Cut a piece of scale leaf from a big onion (a). 2 Remove the translucent epidermis from the inside of the scale leaf using a scalpel. 3 Add a drop of distilled water at the centre of the slide and lay the onion epidermis on the water (b). 4 Using a mounting needle, cover the onion epidermis with a cover slip by placing it at a 45° angle to the slide and slowly press it down. The temporary slide of this specimen is named as wet mount. Make sure there are no air bubbles trapped in the wet mount slide (c) and the onion epidermis is not folded. 5 Add a drop of iodine solution on one side of the cover slip. Place the filter paper at the opposite end of the cover slip to draw the iodine solution to absorb and stain the entire onion epidermis. This technique is known as the irrigation technique (d).

bawang besar bawang besar one bigepidermis onion epidermis epidermis

(a)

mounting needle jarum tenggek cover kacaslip penutup kaca penutup

forseps forseps dermis epidermis

setitis air

(b)

(b)



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(b)

setitis drop ofairdistilled waterair setitis

(b) larutan iodin(b) iodine larutansolution iodin

filter paper

setitis air



forseps epidermis epidermis epidermis

glass slide

(a) (a) jarum tenggek

jarum tenggek jarum kaca penutup tenggek kaca penutup

a pair of forseps forceps

(c)

(c) (c) Preparation of plant cell slide

larutan iodin larutan iodin

Take Note! Air bubbles that are (c) (c)trapped under the

(d) (d)

cover slip can be removed by gently tapping the cover slip with the tip of a sharp pencil.

(d)

(d)(d)

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6 Use a piece of filter paper to absorb excess iodine and distilled water.

CHAPTER 2

7 Observe the slide through a light microscope with a low-power objective lens and then with a high-power objective lens. 8 Draw the epidermal cells structure that can be observed and label it completely. Record the magnification power.

Discussion 1 What are the components of the cell that can be observed through the light microscope? 2 Does a plant cell have a fixed shape? 3 Name another type of plant that can be used in this activity to replace the onion.

Conclusion Suggest a suitable conclusion for this observation.

Using the same slide preparation method, prepare a slide of cheek cells (slide of animal cells) using a methylene blue solution.

Activity itcA 1.s2eitiv2.2

Preparing and examining slides of animal cells

Observation

Materials Animal cell (cheek cell), methylene blue solution, distilled water, filter paper and toothpick

Apparatus Glass slides, cover slips, light microscope, dropper and mounting needle

Procedure 1 Gently scrape the inside of the cheek with a blunt tooth pick. 2 Transfer the scrapping into a drop of water on a clean glass slide and cover with the cover slip. 3 Stain the cheek cells with methylene blue solution using the irrigation technique. 4 Examine the cheek cells through a light microscope. Draw the cheek cells that can be observed. Record the magnification power.

methylene blue solution

filter paper

Preparation of animal cell slide

Discussion 1 What are the components of the cell that can be observed through the light microscope? 2 Does the human cheek cell have a permanent shape? 3 Can you see dark blue spots on the prepared cheek cell? 4 What are the similarities between animal cells and plant cells? Which component is present in the onion cell but is not present in the cheek cell?

Conclusion Suggest a suitable conclusion for this observation.

2.1.1

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Components of animal and plant cells and their functions MITOCHONDRION (PLURAL: MITOCHONDRIA) •

It is rod-shaped or spherical



It consists of two layers of membranes, which are the smooth outer membrane and folded inner membrane



Contains enzymes that play a role in cellular respiration

Function: •

A site that generates energy through the glucose oxidation process during cellular respiration



Energy released in the form of ATP molecules (adenosine triphosphate) to be used by the cells cytoplasm

CENTRIOLE •

Small cylindrical components that exist in pairs in animal cells



Made up of complex arrangement of microtubules



Does not exist in plant cells

lysosome

mitochondrion

nucleus nucleolus

centriole Golgi apparatus

Function: Forms spindle fibre during cell division in animal cells

GOLGI APPARATUS •

Consists of a stack of parallel flattened sacs that are coated by a single cell membrane



New membrane is added at one end of the Golgi apparatus and vesicles bud off from the other end.

Function:

ribosome

Processes, modifies, packs and transports chemicals such as protein, carbohydrate and glycoprotein (combination of carbohydrate and protein)

rough endoplasmic endoplasmic reticulum reticulum

plasma membrane smooth

FIGURE 2.1 Animal cells

PLASMA MEMBRANE •

Outer membrane that surrounds the entire content of cell



Made of proteins and phospholipids



Thin and elastic film



Partially permeable

Function:

outer environment plasma membrane cytoplasm



Separates content of cell from the external environment



Controls movement of substances into and out of the cell



Allows exchange of nutrients, respiratory gases and waste materials between cells and their surroundings

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LYSOSOME Small spherical sac enclosed in a single membrane



Contains hydrolytic enzymes

lysosome CHAPTER 2



Function: •

Hydrolyses complex organic molecules such as protein, nucleic acid and lipid



Breaks down bacteria and components of damaged cells

NUCLEUS (PLURAL: NUCLEI)

RIBOSOME



Largest component in the cell



Small, compact and spherical granules



Spherical, compressed and enclosed in a nuclear membrane with many pores



Consists of protein and ribonucleic acid (RNA)



The nucleus contains chromosomes, nucleolus and nucleoplasm.



Ribosomes are present on the surface of the rough endoplasmic reticulum or exist freely in the cytoplasm.

Function: •

Controls all cell activities

Function:



Has chromosomes that contain deoxyribonucleic acid (DNA). DNA determines the cell characteristics and metabolic function.



nuclear membrane

Site for protein synthesis ribosome

nucleoplasm nucleolus

chromatin

ENDOPLASMIC RETICULUM •

Consists of a system of interconnected folded flattened sacs



Endoplasmic reticulum membrane is continuous with the nuclear membrane.



There are two types of endoplasmic reticulum:





Rough endoplasmic reticulum has ribosomes attached to the surface





Smooth endoplasmic reticulum does not have ribosomes

Function: •

The transport system within the cell



Provides a wide surface for enzyme attachment and biochemical reactions



The rough endoplasmic reticulum transports proteins synthesised by ribosomes.



The smooth endoplasmic reticulum synthesises and transports glycerol and lipids, and carries out the detoxification of drugs and metabolic by-products.

2.1.3

2.1.4

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smooth endoplasmic reticulum

rough endoplasmic reticulum

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CHLOROPLAST

VACUOLE •

Liquid-filled sac, which is the cell sap.



Oval shaped



A vacuole is surrounded by the tonoplast membrane.



Consists of two layers of membrane



Contains chlorophyll pigments in the grana that give plants a green colour



Young plant cells have many small vacuoles while mature plant cells have a large vacuole.



The vacuole in animal cells is small.



Cell sap contains water, organic acids, sugars, amino acids, enzymes, mineral salts, oxygen, carbon dioxide and metabolic by-products.

Function: •

Water is absorbed into the vacuole plant cell and the cell becomes turgid.



In unicellular animals, the vacuole contracts during osmoregulation, osmosis and excretion.

vacuole

tonoplast

chloroplast

Function: Chlorophyll absorbs sunlight and converts it to chemical energy during photosynthesis.

nuclear membrane vacuole

nucleolus nucleus

chloroplast

endoplasmic reticulum

CYTOPLASM •



Consists of a jelly-like medium that contains components of the suspended cells Contains organic compounds (such as protein, lipid and carbohydrate) and inorganic compounds (such as potassium ions)

cytoplasm Golgi appratus

mitochondrion

cell wall plasma membrane FIGURE 2.2 Plant cell

Function: Acts as a medium for biochemical reactions in cells cytoplasm

CELL WALL •

A strong and rigid outer layer



Made from cellulose fibre



Fully permeable

Function:

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Maintains the shape of plant cells



Provides mechanical support to plant cells

cytoplasm plasma membrane cell wall 2.1.3

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CHAPTER 2

Compare and contrast the components of animal cells and plant cells You have learned about the components in animal and plant cells. What are the similarities and differences between the components in animal and plant cells?

cell wall nucleus cytoplasm nucleus

cytoplasm

plasma membrane

plasma membrane vacuole PHOTOGRAPH 2.1 Structure of plant and animal cells through a light microscope

SIMILARITIES Both cells are made of nucleus, cytoplasm, plasma membrane, Golgi apparatus, mitochondrion, endoplasmic reticulum and ribosomes.

PLANT CELLS

DIFFERENCES

ANIMAL CELLS



Has a fixed shape



Does not have a fixed shape



Has a cell wall



Does not have a cell wall



Has chloroplasts



Does not have chloroplasts



Has a large vacuole



No vacuole/if present, it is small



Stores carbohydrate in the form of starch





Does not have a centriole

Stores carbohydrate in the form of glycogen



Has centrioles

Formative Practice

2.1

1 State one structural difference between the rough endoplasmic reticulum and the smooth endoplasmic reticulum. 2 Why is the use of an electron microscope important in studying cells?

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3 Chloroplast is found in some plant cells only. Give one example of a plant cell that does not have chloroplast and give your reasons. 4 Compare and contrast animal cells and plant cells.

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2.2 ICT 2.1 Activity: Studying the life processes of unicellular organisms

pseudopodium

Living Processes in Unicellular Organisms Unicellular organisms are made up of only one cell. However, this cell is a complete unit of life like multicellular organisms. Unicellular organisms carry out all life processes: respiration, movement, nutrition, responding to stimulus, reproduction, growth and excretion. Protozoans are the simplest form of unicellular organisms. Examples of protozoa are Amoeba sp. and Paramecium sp. Let us look at the life processes of Amoeba sp. and Paramecium sp.

vakuol makanan

MOVEMENT

• Amoeba sp. constantly changes its shape when it encounters obstacles. Amoeba sp. moves by extending out its pseudopodium (false feet). This is followed by the flow of cytoplasm into the extended pseudopodium.

RESPONDING TO STIMULI

Amoeba sp. and Paramecium sp. respond to stimuli such as chemicals, touch or bright light by moving away from the stimuli.

endoplasma

• Paramecium sp. moves using rhythmic cilia beats.

RESPIRATION ektoplasma NUTRITION 1 Amoeba sp. moves towards food by extending its pseudopodium to trap food particles by phagocytosis (Figure 2.3). For Paramecium sp. the presence of cilium beat helps transfer food particles into the oral groove.

Exchange of oxygen and carbon dioxide gases occur through the plasma membrane by simple diffusion on the surface of the cell.

nukleus

membran food plasma

1

vakuol mengecut

2

2 The food vacuole is combined with lysosome. The food particles are hydrolysed by the enzyme lysozyme in the lysosomes.

pseudopodium

3 The nutrients are absorbed into the cytoplasm. 4 Undigested food is discharged when the Amoeba sp. moves. Undigested food in the Paramecium sp. is discharged through the anus.

GROWTH Ameoba sp. and Paramecium sp. grow by synthesising new cytoplasm.

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lysosome

food vacuole

3

4

digested food nutrients absorbed

undigested food

FIGURE 2.3 Nutrition in Amoeba sp. 2.2.1

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EXCRETION • Waste such as carbon dioxide and ammonia are removed by diffusion. • As Amoeba sp. and Paramecium sp. live in freshwater environments, water will diffuse by osmosis and fill the contractile vacuole. • When the vacuole expands to the maximum size, contraction occurs and water is excreted from time to time. • This process is called osmoregulation.

plasma membrane

• When the conditions are suitable and there is plenty of food, Amoeba sp. and Paramecium sp. will reproduce via asexual reproduction that is binary fission through mitosis.

CHAPTER 2

REPRODUCTION

Binary fission

• However, when the environmental conditions are not suitable, such as dry conditions, low temperature and food shortage, Conjugation the Amoeba sp. forms spores that will only germinate when the environment improves. • For Paramecium sp., sexual reproduction, that is conjugation occurs when environmental conditions are not suitable.

nucleus contractile vacuole

cilium

food vacuole pseudopodium

oral groove

PHOTOGRAPH 2.2 Amoeba sp. PHOTOGRAPH 2.3 Paramecium sp.

Formative Practice

2 How does the Amoeba sp. move? 3 How does the Amoeba sp.

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nucleus

2.2

1 What is the function of the contractile vacuole in a Paramecium sp.?

2.2.1

anus

contractile vacuole

reproduce when the environment is unfavourable? 4 Predict what will happen to the contractile vacuole if the Paramecium sp. is placed in a concentrated salt solution.

Activity Zone Conduct an experiment using a light microscope to examine the living processes of unicellular organisms.

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2.3 MUSCLE CELL • Arranged as multinuclear striated fibres • Contract and relax to generate movement

WHITE BLOOD CELL shape • Can change • Can change shape • Functions in destroying pathogens

RED BLOOD CELL • Does not contain a nucleus • Shaped as a biconcave disc • Functions to optimise transportation of oxygen

Living Processes in Multicellular Organisms There are various types of cells in multicellular organisms which are different in size, shape and arrangement. The cell structure correlates to its function, and each type of cell is specialised to carry out a specific function. Photographs 2.4 and 2.5 show several types of specialised cells found in humans and plants as well as how these cells are adapted to carry out their respective functions.

NERVE CELL • Long and thin in shape • Functions in sending nerve impulses

EPITHELIAL CELL • Thin and flat cells • Coats the surface of organs such as the digestive tract

SPERM CELL • Has a long tail to enable it to swim towards the ovum in the Fallopian tube • The head carries a set of chromosomes from the male

PHOTOGRAPH 2.4 Several types of human cells that undergo specialisation to carry out different functions

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2.3.1

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SIEVE TUBE ELEMENT

XYLEM VESSEL

ICT 2.2 Activity: Observe plant tissue and animal tissue slides through a light microscope

• Long, continuous hollow tube

• Transports organic materials from leaves to storage organs such as fruits

• Functions in transporting water and mineral salts from the roots to the other parts of the plant

CHAPTER 2

• Long cylindrical tubes arranged from end to end

PALISADE MESOPHYLL CELL

Cross section of leaf

• Consists of long cylindrical cells, arranged vertically and close to each other • Contains high chlorophyll density • This arrangement allows maximum absorption of sunlight for photosynthesis

SPONGY MESOPHYLL CELL • Cells are loosely arranged with lots of air space in between • Large air space allows exchange of gas from the inside of the leaves to the palisade mesophyll cells

GUARD CELL • Modified lower epidermal cells with the thicker cell wall on the inner side

PHOTOGRAPH 2.5 Certain types of plant cells undergo specialisation to carry out different functions

• Controls the opening and closing of the stoma. Stoma is the opening that allows the exchange of oxygen and carbon dioxide

ROOT HAIR CELL • Has a long projection which adds surface area for the absorption of water and mineral salts 2.3.1

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Cell organisation in humans You have learned that multicellular organisms (such as humans) consist of different types of cells with specific functions. How are these cells arranged to form a complex organism? Tissues are a group of cells that have the same structure and function and are arranged together to carry out a specific function. In organisms, tissues can be classified into four different types which are epithelial tissue, muscle tissue, nerve tissue and connective tissue.

Epithelial tissue Epithelial tissue covers the outer surface (skin) and hollow surfaces in the body (digestive tract and respiratory tract) (Figure 2.4). The epithelial tissue structure is adapted based on its function. For example, the epithelial tissue on the skin protects against infections, injuries, chemicals and dehydration. Epithelial tissues that coat the trachea have projections like hair, known as cilia (singular: cilium).

Epithelial tissue covers the surface of the mouth and oesophagus

Epithelial tissue covers the surface of lungs, body cavities and blood vessels

Epithelial tissue covers the surface of the trachea and bronchus

Epithelial tissue lines tubules, glands and kidney ducts

Epithelial tissue covers the small intestine FIGURE 2.4 Types of epithelial and muscle tissues

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2.3.1

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There are three types of muscle tissue: smooth muscle (found in the digestive tract, blood vessel, urinary tract and reproductive tract), skeletal muscle (found in legs and hands) and cardiac muscle (found in the heart wall) (Figure 2.4).

CHAPTER 2

Muscle tissue

Contraction and relaxation of smooth muscle enable involuntary activities such as peristalsis along the digestive tract.

Skeletal muscle is involved in controlled movement. Skeletal muscles contract and relax to generate movement in bones and limbs.

Cardiac muscle builds walls of the heart that contract to pump blood to the whole body. Cardiac muscle contraction is involuntary.

Nerve tissue Nerve tissue is made of neuron or nerve cells (Photograph 2.6). Each neuron consists of a cell body and nerve fibre called dendrite and axon. Nerve tissues can detect stimuli and then send information in the form of an electrical signal (nerve impulses) to the muscles or glands. Nerve tissue regulates and controls body activity.

2.3.1

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PHOTOGRAPH 2.6 Nerve tissue

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Connective tissue The connective tissue consists of various types of tissues and fibres (Figure 2.5). This tissue is distributed all over the body and has many functions. One of its functions is to link the organs. ICT 2.3 Activity: Discuss the importance of cell specialisation in multicellular animals and plants

white blood cell

BLOOD TISSUE Blood plays a functional role in regulation, transportation and protection.

LOOSE CONNECTIVE TISSUE It links the epithelial tissue to the tissue below it, and fixes the organs in their positions.

red blood cell

BONE Bone forms the body frame and protects the internal organs.

FIBROUS CONNECTIVE TISSUE These tissues form tendons and ligaments. The tendon connects bones and muscles while the ligaments connect bones to bones.

ADIPOSE TISSUE Connective tissues keep fat under the skin dermis and the surface of all main organs.

CARTILAGE Cartilage encloses bone tips to prevent the bone from wearing out.

nucleus collagen fibres

FIGURE 2.5 Connective tissue

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Tissue organisation in plants CHAPTER 2

Tissue organisation in plants is summarised in Figure 2.6. PLANT TISSUE

Meristem tissue

Permanent tissue

Lateral meristem tissue

Apical meristem tissue

Dermal tissue

Ground tissue

Parenchyma tissue Collenchyma tissue

Vascular tissue Xylem tissue Phloem tissue

Sclerenchyma tissue FIGURE 2.6 Tissue organisation in plants

PARENCHYMA TISSUE Functions to store starch, protein and water. This tissue can also carry out photosynthesis.

PHOTOGRAPH 2.7 Meristem tissue at the tip of the root

COLLENCHYMA TISSUE Functions in giving support to young, non-woody stems (herbaceous plants).

SCLERENCHYMA TISSUE Functions in providing support and mechanical strength to all mature parts of the plant.

2.3.1

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PHOTOGRAPH 2.8 Different types of ground tissues

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xylem vessel

VASCULAR TISSUE Vascular tissues are made up of xylem tissue and phloem tissue.

XYLEM TISSUE

PHLOEM TISSUE

The xylem functions in transporting water and mineral salts from the roots to other parts of the plant. Ligneous xylem tissue wall provides support and mechanical strength to the plants.

The phloem functions in transporting organic matters such as sucrose from the leaves to all parts of the plant. sieve tube

Density of certain cell components and specialised cell functions Since the functions performed by cells are different, some cells have a higher density of certain cell components. The density of a cell component in a particular cell is related to the specific function of the cell. Table 2.1 provides examples of cells that have a higher density of certain cell components. TABLE 2.1 Relationship between cell component density with specialised cell functions

Types of cell

Cell component found in abundance

Sperm cell

Muscle cell such as flight muscle cells in insects and birds

Requires a lot of energy to swim towards the uterus and Fallopian tube to fertilise the secondary oocytes Mitochondrion

Plant meristem cell

Chloroplast Spongy mesophyll cell Pancreatic cell

Liver cell

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Requires a lot of energy to contract and relax to enable movement and flight Requires a lot of energy to carry out active cell division process to produce new cells

Palisade mesophyll cell

Goblet cell in intestinal epithelium and respiratory tract

Function

Absorbs more sunlight to carry out the process of photosynthesis Increases synthesis and secretion of digestive enzymes

Rough endoplasmic reticulum

Produces mucus

Golgi apparatus •

Metabolises carbohydrates



Detoxification of drugs and poisons 2.3.3

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Formative Practice

2.3

1 State the components of cells found in high density in cells that secrete protein products.

3 Explain why the palisade mesophyll cell contains a lot of chloroplast.

2 Briefly describe the structure and function of the nerve tissue.

4 Fat cells have three adaptive characteristics to allow the storage of fat. Describe the three characteristics.

2.4

CHAPTER 2

All cell components perform their respective functions to ensure that the cells function at the optimum level. The collaboration of all the components of the cells is similar to a factory with different parts and each with its specific function. What happens to the cell if there is a deficiency, absence or failure in any of the cell components such as lysosomes, mitochondrion, chloroplasts or ribosomes? Failure of the mitochondrion function or a mitochondrion disjunction can cause stunted growth, weak muscles, hearing and vision problems. Tay-Sachs is a hereditary disease caused by the failure of enzymes to produce in the lysosomes. Tay-Sachs patients will experience stunted growth and mental retardation.

Levels of Organisation in Multicellular Organisms epith elia l

tiss

ue

cardia c m u s c l e ti s s u e

A group of different tissues combine to form organs. Organs perform special functions as a result of the combination of tissues that form the organ. For example, the heart organ is composed of epithelial tissue, cardiac muscle tissue, connective tissue and nerve tissue. The epithelial tissue fills up space in the heart. Cardiac muscle tissue functions in pumping blood to the rest of the body. Connective tissues such as the blood, connect the systems in the organ. Nerve tissue regulates the rhythm of the heartbeat.

heart

ne

rve

tiss

ue

ti ve ecti n n co

e s su

PHOTOGRAPH 2.9 Tissues that form the heart organ 2.3.4

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Each multicellular organism is made up of many organs. Different organs work together to carry out a specific function to form an organ system. There are 11 main organ systems in the human body (Figure 2.7), which are the respiratory system, digestive system, blood circulatory system, lymphatic system, nervous system, integumentary system, endocrine system, skeletal system, muscular system, urinary system and reproductive system.

ENDOCRINE SYSTEM • The endocrine gland that secretes hormones Main function • Coordinates body activities with the nervous system

RESPIRATORY SYSTEM • Trachea, nose, lungs and diaphragm Main function • Exchange of oxygen and carbon dioxide gases between the body and external environment

MUSCULAR SYSTEM • Skeletal muscles, smooth muscles and cardiac muscles Main function • Contracts and relaxes to produce movements in different parts of the body

MALE REPRODUCTIVE SYSTEM • Testes, prostate gland and penis Main function • Produces sperm and male sex hormone

LYMPHATIC SYSTEM • Spleen, lymph nodes and lymph vessels Main function

FEMALE REPRODUCTIVE SYSTEM • Ovary, uterus, Fallopian tube, vagina and cervix

• Maintains balance of bodily fluids and prevents infectious diseases

Main function • Produces ovum and female sex hormones

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FIGURE 2.7 Main organ systems in the human body 2.4.1

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• Brain, spinal cord and peripheral nerves Main function • Detects and sends information in the body, as well as coordinates body activities

BLOOD CIRCULATORY SYSTEM • Heart, artery, vein and blood capillary Main function

Cell Tissue Organ System

All the organ systems are coordinated and collaborated as one complete organism. The sequence of the organisation of cells in a multicellular organism is shown in Figure 2.8.

CHAPTER 2

NERVOUS SYSTEM

Multicellular organism

• Transports nutrients, respiratory gases and waste products

DIGESTIVE SYSTEM • Mouth, oesophagus, stomach, liver, pancreas, small intestine and large intestine

Cell

Main function • Digests food into a simpler form for easy absorption

Tissue

URINARY SYSTEM • Kidney, ureter, urethra and bladder Main function • Eliminates waste products such as urea and uric acid from the body

SKELETAL SYSTEM Organ

• Bone, cartilage, ligament and tendon Main function • Supports the body, protects the internal organs and provides a base for muscle adhesion

System

INTEGUMENTARY SYSTEM • Skin Main function • Protects the body from physical injury, infection and dehydration 2.4.1

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Multicellular organism

FIGURE 2.8 The sequence of the organisation of cells in human beings

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leaf fruit flower

shoot system

stem root root system

The plant system is divided into the shoot system and the root system (Figure 2.9). • The shoot system consists of stems, leaves, shoots, flowers and fruits. • Stems and twigs are support systems that support the leaves at a vertical position to allow maximum absorption of sunlight during photosynthesis. • Flowers are involved in the pollination process. • The root system consists of all roots in a plant that function in absorbing water and mineral salts as well as providing support for plants.

FIGURE 2.9 Two main systems in plants

Formative Practice

2.4

1 State arrangement of sequence in the organisation of cells in a multicellular organism.

3 Stems, twigs and flowers are organs in a plant. Describe how stems, twigs and flowers function in the shoot system.

2 The skin is the largest organ in the body. Why is skin classified as an organ?

4 Predict what will happen if the organisation level of cells does not exist in an organism.

Summary CELL BIOLOGY AND ORGANISATION

Cell Structure and Function Cell components • Nucleus • Mitochondrion • Ribosome • Centriole • Golgi apparatus • Chloroplast • Cell membrane • Cell wall • Vacuole • Cytoplasm • Lysosome • Rough endoplasmic reticulum • Smooth endoplasmic reticulum

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Living Processes in Unicellular Organisms

Amoeba sp. and Paramecium sp. • Movement • Response to stimuli • Nutrition • Respiration • Growth • Excretion • Reproduction

Living Processes in Multicellular Organisms Relationship between specific cell structure and cell function

Levels of Organisation Cell Tissue Organ System Organism

Relationship between cell component density and cell function Effect of the absence of cell components to the cell 2.4.2

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Have you mastered the following important concepts? • Structure and function of animal cells and plant cells • Similarities and differences bet ween animal cells and plant cells • Living process of unicellular organism • Living process of multicellular organism • Relationship bet ween cell component densit y in a cell and its specific function • Effect of the absence or failure of the cell component function in multicellular organisms • Sequence of levels of organisation in multicellular organisms • Organ systems with its main functions in multicellular organisms

CHAPTER 2

Self Reflection

Summative Practice 2 1 Why is chloroplast only found in plant cells and not in animal cells? 2 Explain the asexual reproduction of Amoeba sp. 3 An aphid is a small insect which sucks sap in plants. An aphid puts its mouth in the stem of a plant and sucks its nutrients. Name the liquid obtained from the plant and explain why aphids are mostly found in the daytime. 4 Figure 1 shows a plant cell.

P P



FIGURE 1



State the characteristics of P and its function.

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5 X is a digestive organ consisting of cells with a high concentration of rough endoplasmic reticulum for protein digestion. What is X? Explain your answer. 6 Plant cells undergo process X to form xylem vessels. Name process X. Explain how xylem vessels are specialised in transporting water and mineral salts. 7 Arif is a farmer. He uses a weed killer to control the weed population growth on his farm. Weed killers can stop the transportion of certain minerals in plants through the hair root tissue. Explain why. 8 Explain how an Amoeba sp. can survive in fresh water that is hypotonic to the cytoplasm of the organism. 9 Figure 2 shows one cell that can be seen through an electron microscope.

(a) (i) Name structure K. (ii) State the function of structures K and N.



(b) Explain how L mantains the turgidity of the cell.

N

10 State the differences between the following: (a) meristematic tissue with plant epidermal tissue, (b) cell and tissue, (c) epithelial tissue and muscle tissue.

L K

11 Figure 3 shows the structure of a leaf.

FIGURE 2 R

P S

Q

FIGURE 3

(a) Name the cells labelled P and R. (b) State the functions of cells P and R. (c) Explain the role of cell Q in increasing the rate of photosynthesis. (d) S contains two types of tissue. (i) Name the two tissues.

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(ii) Explain the adaptive features of tissues in S that help in the transportation of materials in plants. CHAPTER 2

Essay Questions 12 Using an example of a unicellular organism, explain the five living processes of this organism. 13 Figure 4 shows a unicellular organism that lives in a fresh water pond.

X

FIGURE 4

(a) Explain the function of X in osmoregulation. (b) Predict what will happen if a cell does not have a Golgi apparatus. Explain your answer. (c) For each of the following cell, explain the relationship between structure and function.

(i)

Enrichment

(ii)

cell P

cell Q FIGURE 5

14 Many cancers start with the epithelial tissue. This includes lung cancer, colon cancer and skin cancer. What are the two characteristics of this tissue that can cause cancer? 15 The damage to the cartilage disc between the vertebrae of the spine is difficult to repair by their own cells. What is the latest technology that can be used to develop new cartilage tissues? Complete answers are available by scanning the QR code provided

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3

CHAPTER

Movement of Substances Across the Plasma Membrane

What is the association of carrier protein on plasma membrane with genetic diseases such as hyperkalemic periodic paralysis (HYPP) in horses?



Do you KNOW...

What is the fluid m osaic model? • What are the ch aracteristics of substances that are able to move across the plasma membrane? • What are the ex amples of passive and active transport? • How do you ap ply the concept of movement of su bstances in everyday life?

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3.1 Structure of Plasma Membrane 3.1.1 Justify the necessity of movement of substances across a plasma membrane. 3.1.2 Describe the components of a plasma membrane and its function based on the fluid mosaic model. 3.1.3 Draw and label the components of a plasma membrane based on the fluid mosaic model. 3.1.4 Describe the permeability of a plasma membrane. 3.2 Concept of Movement of Substances Across a Plasma Membrane 3.2.1 State the characteristics of substances that are able to move across a plasma membrane in these aspects: • size of molecules • polarity of molecules • ionic charge 3.2.2 Conduct experiments to study the movement of substances across a selectively permeable membrane by using: • Visking tubing • simple osmometer 3.2.3 Describe by using examples movement of substances across a plasma membrane: • passive transport • active transport 3.2.4 Compare and contrast passive transport and active transport.

3.3.4 Design an experiment to study the effects of different concentrations of solution on animal and plant cells. 3.3.5 Communicate about the effects of hypotonic, hypertonic and isotonic solutions on cell based on movement of water molecules: • animal cell • plant cell 3.4 Movement of Substances Across a Plasma Membrane and its Application in Daily Life 3.4.1 Conduct an experiment to determine the concentration of cell sap of a plant tissue. 3.4.2 Correlate the concentration of cell sap in a plant tissue with the phenomenon of plant wilting. 3.4.3 Explain by using examples the application of the concept of movement of substances across a plasma membrane in daily life. 3.4.4 Communicate about reverse osmosis in water purification

3.3 Movement of Substances Across a Plasma Membrane in Living Organisms 3.3.1 Explain by using examples the process of passive transport in organisms. 3.3.2 Explain by using examples the process of active transport in organisms. 3.3.3 Define solution: • hypotonic solution • hypertonic solution • isotonic solution

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3.1 ICT 3.1 Activity: To discuss the need for movement of substances across the plasma membrane

Activity Zone

Structure of Plasma Membrane The necessity of movement of substances across a plasma membrane

Living cells require substances from the external environment to carry out living processes. At the same time, the metabolic processes in cells produce waste that need to be disposed of from the cells. What are the substances required by cells and the waste products of cells? How do these substances move in and out of cells? Cells must allow some substances to move into and out of the cells to maintain the living processes. The movement of substances into and out of the cell is regulated by the plasma membrane. Before you learn about how substances move across the plasma membrane, let us look at its structure.

Structure of the plasma membrane

Draw a model of the plasma membrane and its related components.

In Chapter 2, you have learned that each cell is enclosed in a thin plasma membrane which separates the living cell from its environment. According to the fluid mosaic model, protein molecules float within the phospholipid bilayer, forming a mosaic pattern that changes frequently. A polar Figure 3.1 shows the plasma membrane. head which is hydrophilic

EXTRACELLULAR carrier proteins

glycolipid

Phospholipid A nonpolar tail which is hydrophobic

glycoprotein

phospholipid bilayer

channel protein

CYTOPLASM

cholesterol

FIGURE 3.1

Plasma membrane

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There are various types of protein molecules embedded partially or fully within the membrane. The protein molecules are widely dispersed between the phospholipid bilayer. The protein molecules with channels or canals are known as channel proteins, whereas the protein molecules that function as carriers are called carrier proteins (Figure 3.2). Extracellular

Extracellular

pore

Biological Lens There were many plasma membrane models proposed by scientists. However, the fluid mosaic model proposed by S. J. Singer and G. L. Nicholson in 1972 is the accepted model by scientists today.

CHAPTER 3

Each phospholipid molecule consists of: • A polar head which is hydrophilic (attracted to water) • A nonpolar tail which is hydrophobic (repels water) The heads of the phospholipid molecule in the outer layer face the extracellular fluid, whereas the phospholipid heads in the inner layer face the cytoplasm. The tails of the phospholipid molecule of the two layers face each other.

molecule

molecule

Cytoplasm

Cytoplasm channel protein

carrier protein

FIGURE 3.2 Models of channel and carrier proteins

Some proteins and lipids have carbohydrate chains attached to them, known as glycoprotein and glycolipid respectively (Figure 3.1). Glycoprotein and glycolipid act as receptors to hormones such as insulin, stabilise the membrane by forming hydrogen bonds with water and act as antigens for cell identification. There are also cholesterol molecules found between the phospholipid molecules (Figure 3.1). Cholesterols make the phospholipid bilayer stronger, more flexible and less permeable to water-soluble substances such as ions. The phospholipid bilayer, proteins and cholesterols are not static but form a dynamic and flexible structure. This contributes to the ‘fluid’ characteristic of the plasma membrane and makes the plasma membrane more flexible.

3.1.2

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Millennial Career Biochemists who specialise in cell and molecular biology can work in the pharmaceutical industry, biotechnology and forensics.

Permeability of a plasma membrane A membrane is said to be permeable to a substance if the membrane allows the substance to pass through it freely. On the contrary, a membrane is impermeable if a substance is unable to move across it. The plasma membrane is a selectively permeable membrane. What does selectively permeable membrane mean? Selectively permeable membrane only allows free movement of certain molecules across it, and prevent or limit the movement of other substances. The plasma membrane has a selectively permeable property due to its building structure. The phospholipid bilayer and protein determine the membrane permeability towards specific substances. We will learn about the characteristics of substances that are able to move across the plasma membrane in the next unit.

Formative Practice

3.1

1 What are the two main components of the plasma membrane? ICT 3.2 Video: Fluid mosaic model of a plasma membrane (Accessed on 21 August 2019)

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2 Explain the meaning of fluid mosaic model. 3 Predict what will happen to the plasma membrane if there is no cholesterol. 4 Explain the role of phospholipid and protein in ensuring the permeability of the plasma membrane.

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3.2

CHAPTER 3

Concept of Movement of Substances Across a Plasma Membrane The characteristics of substances that are able to move across a plasma membrane There are three common factors that determine whether a molecule can pass through a plasma membrane, which are molecule size , polar molecule and ionic charge.

ICT 3.3 Video: Movement of molecules and ions across the plasma membrane (Accessed on 21 August 2019)

CHARACTERISTICS OF MOVEMENT OF SUBSTANCES ACROSS A PLASMA MEMBRANE

LIPID-SOLUBLE SUBSTANCES

Nonpolar molecules

LIPID INSOLUBLE SUBSTANCES

SMALL MOLECULE AND ION

Examples: • Fatty acid • Glycerol • Fat soluble vitamins (A, D, E, K) • Steroid compounds

LARGE MOLECULE

• Polar molecules (Example: water)

Examples:

• Nonpolar molecules (Examples: oxygen, carbon dioxide)

• Glucose • Amino acid

• Ion (Examples: K+, Na+, Ca2+, Mg2+)

small molecule and ion

lipid soluble molecule

small nonpolar molecule

Extracellular

H2O

O2

CO2

large molecule

carrier protein H2O

O2

Cytoplasm

CO2

channel protein

FIGURE 3.3 Movement of substances across a plasma membrane 3.2.1

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Conduct the following experiment to show that the movement of substances across a selectively permeable membrane depends on the size of the molecule.

Activity ivitcA 1.2seit3.1

Studying the movement of substances across a selectively permeable membrane

Experiment

Problem statement Does the size of dissolved particles affect the movement of substances across a selectively permeable membrane?

Hypothesis Only small molecules are able to diffuse through a selectively permeable membrane while a large molecule cannot diffuse through a selectively permeable membrane.

Variables Manipulated: Molecule size Responding: Presence of molecules in the Visking tubing and beaker Fixed: Surrounding temperature and soaking time

Materials Benedict’s solution, 1% starch suspension, iodine solution, 30% glucose solution, distilled water, Visking tubing (12 cm) and thread

Apparatus Beaker, test tube, Bunsen burner, dropper and measuring cylinder

Procedure 1 Soak the Visking tubing in water for 5 minutes to soften it. Make a knot and tie one end of the Visking tubing with thread to prevent leaking. 2 Fill the Visking tubing with the 10 ml glucose solution and 10 ml starch suspension. Tie one end of the Visking tubing tightly with a thread. The solution colour is recorded. 3 Rinse the outside of the Visking tubing with distilled water. 4 Add 400 ml of distilled water in a beaker. 5 Place the Visking tubing in the beaker and leave it for 30 minutes. 6 After 30 minutes, remove and transfer the Visking tubing into a dry beaker.

400 ml distilled water

Visking tubing 10 ml glucose solution + 10 ml starch suspension

7 (a) Conduct the iodine test for the solutions in the Visking tubing and in the beaker. Put 2 ml of each solution in separate test tubes and add 1 ml of the iodine solution. Observe the colour produced. (b) Conduct the Benedict’s test on the solutions in the Visking tubing and in the beaker. Put 2 ml of each solution into separate test tubes and add 1 ml of Benedict’s solution. Heat the solutions in a water bath for 5 minutes and record any changes in colour.

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Results

Visking tubing

10 ml glucose solution + 10 ml starch suspension

Beaker

400 ml distilled water

Iodine test

Benedict’s test

CHAPTER 3

Contents

Discussion 1 What molecule is found in (a) Visking tubing (b) beaker? 2 What are the inferences that can be made based on the (a) size of the starch molecule (b) size of the glucose molecule compared to the pore size in the Visking tubing? 3 What are the similarities between a Visking tubing and a plasma membrane?

Conclusion Is the hypothesis accepted? Suggest a suitable conclusion.

the movement of substances across a tivitcStudying A 1.2sei3.2 Activity Visking tubing using a simple osmometer

Experiment

Problem statement How do the water molecules permeate across selectively permeable membranes?

Hypothesis Water molecules permeate from an area of high water potential to an area of low water potential.

Variables Manipulated: Time Responding: Increase in the level of sucrose solution in a capillary tube Fixed: Concentration of sucrose solution

Materials 30% sucrose solution, Visking tubing (12 cm), thread and distilled water

Apparatus Retort stand with a clamp, 25 cm capillary tube, syringe, ruler, 50 ml beaker, marker pen, scissors and stopwatch

Procedure 1 Cut a Visking tubing (12 cm). 2 Soak the Visking tubing in water for 5 minutes to soften it. 3 Tie one end of the Visking tubing tightly using thread to form a bag. 4 Fill the Visking tubing with the 30% sucrose solution using the syringe.

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5 Tightly tie the other end of the Visking tubing to a capillary tube. 6 Rinse the outer part of the Visking tubing with distilled water. 7 Clamp the capillary tube vertically to the retort stand. 8 Immerse the Visking tubing in a beaker containing distilled water.

capillary tube

9 With a marker pen, mark the level of sucrose solution in the capillary tube at the beginning of the experiment.

initial level of sucrose solution

10 Measure and record the level of sucrose solution in the capillary tube for every 2 minutes from the previous level for 12 minutes.

distilled water Visking tubing 30% sucrose solution

11 Plot a graph of the level of sucrose solution (mm) against time (minutes).

Results

Time (minutes)

0

2

4

6

8

10

12

Level of sucrose solution (mm)

Discussion 1 Based on the graph, explain the relationship between the levels of sucrose solution and time. 2 What caused the change in the levels of sucrose solution? 3 What inferences can be made regarding the size of the sucrose molecules and water, and the pore size of the Visking tubing? 4 Predict the results if the experiment is repeated using a Visking tubing filled with distilled water, and a beaker filled with a 30% sucrose solution.

Conclusion Is the hypothesis accepted? Suggest a suitable conclusion.

Our World of Biology Do you know that an egg membrane can be used to replace the Visking tubing? Can you make an egg osmometer?

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The movement of substances across a plasma membrane occurs through passive and active transport.

Passive transport An analogy of passive transport is like riding a bicycle downhill. The process does not involve the use of energy. Simple diffusion, osmosis and facilitated diffusion are examples of passive transport.

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Simple diffusion

high concentration phospholipid bilayer

Simple diffusion

low concentration Solutes: oxygen carbon dioxide

CHAPTER 3

Simple diffusion is the movement of molecules or ions from an area of high concentration to an area of low concentration. The moving molecules are said to move down the concentration gradient until a dynamic equilibrium is achieved. This may occur with or without the presence of a plasma membrane. Lipid soluble molecules (fatty acids and glycerol), oxygen and carbon dioxide diffuse through the phospholipid bilayer as simple diffusion (Figure 3.4).

fatty acids glycerol

FIGURE 3.4 Simple diffusion through the phospholipid bilayer

Osmosis

Osmosis is a passive transport process that is similar to diffusion but it involves only water molecules. Osmosis refers to the net movement of water molecules from an area of high water potential (low solutes concentration) to an area of low water potential (high solutes concentration) randomly through a selectively permeable membrane. The selectively permeable membrane is permeable to water but impermeable to some solutes such as sucrose molecules (Figure 3.5). The same situation occurs in cells through the phospholipid bilayer (Figure 3.6). keupayaan air tinggi keupayaan air rendah kepekatan low waterbahan potential terlarut rendah terlarut tinggi

bahan highkepekatan water potential

Achieved dynamic equilibrium

water molecule high water potential

phospholipid bilayer sucrose molecule water molecule

selectively permeable membrane

FIGURE 3.5 Osmosis

osmosis

low water potential FIGURE 3.6 Osmosis through the phospholipid bilayer

Facilitated diffusion Lipid-insoluble molecules such as ions, large molecules such as amino acids and glucose are unable to pass through the phospholipid bilayer. These substances move across the membrane with the aid of transport proteins (carrier or channel proteins). This process is known as facilitated diffusion. Facilitated diffusion does not require energy because the transport proteins transport molecules down a concentration gradient. The process continues until a dynamic equilibrium is achieved when the concentration of molecules is the same at both sides of membranes. 3.2.3

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CHANNEL PROTEINS form channels or canals to allow small-sized solutes and ions to diffuse across the plasma membrane. Channels have specific internal characteristics that only allow specific ions to pass through it. CARRIER PROTEINS have specific sites and can only bind to a specific molecule. For example, glucose molecules can only bind to the specific site of a glucose carrier protein.

ion

glucose

channel protein channel protein

carrier carrierprotein protein

FIGURE 3.7 Facilitated diffusion through channel and carrier proteins

The process of the movement of glucose molecules across a plasma membrane occurs through a facilitated diffusion (Figure 3.8). Extracellular glucose

Extracellular glucose concentrations are higher than in cytoplasm.

specific site

Glucose binds with the specific site of the carrier proteins.

carrier protein Cytoplasm

Carrier proteins return to their original shape and are ready to transport other molecules.

Carrier proteins change shape to allow glucose molecules to pass through the carrier proteins and to enter the cell. FIGURE 3.8 Facilitated diffusion through carrier proteins

Active transport Movement of substances across a plasma membrane may occur by active transport. The characteristics of an active transport are as follows: • The movement of molecule or ion substances across a plasma membrane occurs against a concentration gradient. • It requires energy from ATP (adenosine triphosphate) molecules generated during cellular respiration. • It requires specific carrier protein with specific sites to bind with certain molecules or ions. • Carrier proteins also possess receptors to bind with ATP molecules. Carrier proteins change shape when a phosphate group attaches to it. As a result, molecules or ions move across a membrane (Figure 3.9). 54

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1

2

Extracellular fluid: High Na+ concentration Na+

+

Na

Na

Na+ Na+ Na+ Na+

Extracellular fluid: Low K+ concentration

Na

Na Na+ Na+

P

ATP

ADP

Na+

Na+

Na+

Na+

Na+

P

Na+

ATP molecules (adenosine triphosphate) decompose into ADP (adenosine diphosphate) and P (phosphate). The phosphate group is bound to the carrier protein.

Phosphate bond provides energy and changes the shape of the carrier protein, then sodium ion is transported through the carrier protein out of a cell.

5

6

K+

K+

+

+

Na+

Three sodium ions bind to the carrier protein.

3

Na+

Na+

Cytoplasm: Low Na+ concentration

4

Na+

+

CHAPTER 3

Active transport results in the accumulation or excretion of molecules or ions in the cell. Carrier proteins involved in active transport are known as pumps. For example, in animal cells, the carrier proteins that transport sodium ions to extracelullar, and potassium ions into the cell are called sodium-potassium pump. The mechanism of the sodium-potassium pump is described in Figure 3.9.

K+

K+ +

K

K+ Cytoplasm: High K+ concentration

K+

+

K +

K

P

+

+

K

Two potassium ions from outside the cell bind with a carrier protein. The phosphate group leaves the carrier protein.

K

+

K

+

K

K+

K+

The loss of the phosphate group restores the original shape of the carrier protein.

K+

K+

K+

Potassium ion is transported through the carrier protein into the cell.

FIGURE 3.9 Sodium-potassium pump

There is another type of pump known as the proton pump. For example, the proton pumps that are found on the epithelial cells lining the stomach cavity. Proton pump causes the acidity of the stomach contents. Energy from the ATP enables the hydrogen ion to be transported by the carrier proteins (proton pump) towards the extracellular fluid. This causes an accumulation of the hydrogen ion and acid production in the stomach cavity. The proton pump mechanism is described in Figure 3.10. 3.2.3

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Extracellular fluid: Low pH High concentration H+ of hydrogen ions

+ +

ATP H+

H+

Carrier protein +

Cytoplasm: High pH Low concentration of hydrogen ions

+ +

H+

H+

H+

FIGURE 3.10 Proton pump

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Energy is not required

Moving a substance across a membrane

Occurs following the concentration of the gradient

Requires energy

PASSIVE TRANSPORT

Occurs until a dynamic equilibrium is achieved

ACTIVE TRANSPORT

Occurs through a selectively permeable membrane

Occurs against the concentration of the gradient There are accumulation and disposal of molecules or ions

FIGURE 3.11 Similarities and differences between passive and active transports

Formative Practice

3.2

1 Give some examples of substances that are able to pass through the phospholipid bilayer. 2 Describe how sodium ions are transported out of the cell. 3 A scientist conducts an experiment by soaking the roots of a plant in a solution which contains mineral salts at different levels of oxygen concentrations. Explain why the mineral salts concentration in the roots increased when the oxygen concentration in the solution increases by 10%.

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CHAPTER 3

3.3

Movement of Substances Across a Plasma Membrane in Living Organisms Active and passive transport in living organisms Where do passive and active transport occur in living organisms?

Passive transport in organisms occurs during:

Active transport in organisms occurs during:

• gaseous exchange between an alveolus and a blood capillary through simple diffusion (Figure 3.12)

• absorption of glucose and amino acids in the villus

• reabsorption of water occurs by osmosis through the renal tubule in the kidney • absorption of water by a plant root hair cell by osmosis (Figure 3.13) • absorption of fructose molecule in the villus by facilitated diffusion air movement blood from pulmonary veins a layer of water

• reabsorption of glucose through the renal tubule in the kidney • transport of sucrose from a leaf to a phloem tissue • absorption of mineral ions by a plant root hair cell (Figure 3.13)

alveolus blood from pulmonary artery

oxygenated blood

mineral ion absorbed into the hair root cell through active transport

blood capillary

O2 oxygen deoxygenated CO2 molecules blood diffuse from the alveolus into the blood capillaries according to the mineral concentration carbon dioxide molecules diffuse from the salts gradient blood capillaries entering the alveoli according to the concentration gradient

water diffuses by osmosis from soil water into the root hair cells

water

FIGURE 3.12 Gaseous exchange at the alveoli occurs by simple diffusion root hair

soil grains

roots

FIGURE 3.13 Absorption of water by osmosis and mineral ions through active transport 3.3.1

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Isotonic, hypotonic and hypertonic solutions Generally, there are three types of solutions: isotonic, hypotonic and hypertonic. As you have learned, diffusion of water occurs by osmosis from an area of high water potential to an area of low water potential across a plasma membrane. The explanation on each solution is summarised in Table 3.1. TABLE 3.1 Isotonic, hypotonic and hypertonic solutions

Concept Isotonic solution

Definition Solution A and B have the same concentrations of solutions.

Explanation selectively permeable membrane selectively permeable membrane

A A

B water B molecules

Solutions A and B are isotonic toward each other. No net movement of water.

water molecule

selectively permeable membrane

solutes

A

Hypotonic solution

Solution A has a low solutes concentration and high water potential.

B water molecule

selectively permeable membrane

A A

BB

Solution A is hypotonic to solution B. Water diffuses from solution A to B by osmosis.

soluble substances A

Hypertonic solution

Solution A has a high solutes concentration and low water potential.

A

A

B

B

B selectively permeable membrane A

B

soluble substances

Solution A is hypertonic to B. Water diffuses from solution B to A by osmosis.

Activity Zone Conduct an experiment to observe the effect of osmosis on an egg plasma membrane.

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The effects of hypotonic, hypertonic and isotonic solutions on animal cells and plant cells

Biological Lens The term haemolysis is only used for the burst of red blood cells.

CHAPTER 3

The cell cytoplasm contains solutes such as glucose and mineral salts. The fluid found in the cell is known as intracellular fluid. Each cell is surrounded by extracellular fluid. Therefore, the cell will always go through the osmosis process and movement of water across the plasma membrane, depending on the water potential of the extracellular fluid and intracellular fluid. EFFECT OF HYPOTONIC SOLUTION

AR



When red blood cells are placed in a hypotonic solution, water will diffuse into the cells by osmosis, causing the cells to swell and finally burst.



This is because the plasma membrane is too thin to withstand the osmotic pressure built up in the cells.



The burst of red blood cells is known as haemolysis.

EFFECT OF HYPERTONIC SOLUTION THE EFFECTS OF HYPOTONIC, ISOTONIC AND HYPERTONIC SOLUTIONS ON ANIMAL CELLS



When red blood cells are placed in a hypertonic solution, water will move out of the cells by osmosis.



This will cause the cells to shrink.



The red blood cells are said to undergo crenation.

EFFECT OF ISOTONIC SOLUTION •

Water diffuses into and out of the cell by osmosis at the same rate.



No net movement of water across the plasma membrane.



The cells maintain their normal shape.

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EFFECT OF HYPOTONIC SOLUTION •

When plant cells are placed in a hypotonic solution, water will diffuse into the vacuoles by osmosis.



This will cause the vacuoles to expand and push the cytoplasm and plasma membrane against the cell wall.



In this condition, the cells are said to be turgid.



Plant cells do not burst because the cell wall is rigid and strong.



Turgor pressure is important to plant cells because it gives support and maintains the shape of cell.



Cell turgidity causes guard cell to swell to allow the stomata to remain open for photosynthesis.

EFFECT OF HYPERTONIC SOLUTION •

When plant cells are placed in a hypertonic solution, water will diffuse out of the vacuoles by osmosis.



Vacuoles and the cytoplasm will shrink, causing the plasma membrane to be pulled away from the cell wall.



This process is known as plasmolysis. Plasmolysis causes leaves and stems to bend downwards and wilt.



Plasmolysed plant cells can regain their turgidity if the cells are returned to a hypotonic solution immediately.



The cells are said to undergo deplasmolysis.

THE EFFECTS OF HYPOTONIC, ISOTONIC AND HYPERTONIC SOLUTIONS ON PLANT CELLS

EFFECT OF ISOTONIC SOLUTION

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When the sap of the plant cell and extracellular solution are isotonic, water potential is the same.



The movement of water diffusion in and out of cells is the same.



Cells become flaccid. 3.3.4

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Activity tivitcA 1.2sei3.3

Studying the effects of hypotonic, hypertonic and isotonic solutions on animal cells

Experiment

Problem statement What is the effect of hypotonic, hypertonic and isotonic solutions on animal cells?

Hypothesis

blood

Hypotonic solution causes the cell to explode. Hypertonic solution causes the cell to shrink. Isotonic solution causes the cell to remain normal.

CHAPTER 3

• • •

Variables Manipulated: Concentration of surrounding solution Responding: Chicken blood cells condition Fixed: Surrounding temperature and types of cell

filter paper

Take Note!

Materials Fresh chicken blood, 0.15 M and 0.50 M sodium chloride solutions, filter paper and distilled water

Apparatus Light microscope, glass slide, dropper, mounting needle and cover slip

Red blood cells from the chicken are kept in sodium chloride solution to prevent blood clot.

Procedure 1 Prepare four slides and label as A, B, C and D. 2 Place a drop of fresh chicken blood on slide A and put a cover slip onto it. 3 Observe the shape of the red blood cells under a light microscope. 4 Put a drop of distilled water on slide B and cover with a cover slip. 5 Add a drop of blood on the edge of one side of the cover slip. At the same time, place a filter paper at the opposite side of the cover slip to spread the blood beneath the cover slip. 6 Examine the slide under a light microscope and draw the shape of the red blood cells in the table below. 7 Repeat steps 4 to 6. Replace the distilled water with 0.15 M sodium chloride solution (slide C) and 0.50 M sodium chloride solution (slide D).

Results

Slide

Observation

Labelled drawing of cell shape

A (red blood cells) B (red blood cells in distilled water) C (red blood cells in 0.15 M sodium chloride solution) D (red blood cells in 0.50 M sodium chloride solution)

Discussion 1 Discuss and explain the results obtained for each slide. 2 Which solution is hypotonic, hypertonic and isotonic to the red blood cells? 3 What happened to the red blood cells in slides B and D?

Conclusion Is the hypothesis accepted? Suggest a suitable conclusion.

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Activity itivitcAStudying the effects of hypotonic, hypertonic 1.2 se3.4 and isotonic solutions on plant cells

Experiment

Problem statement What is the effect of different solution concentrations on plant cells?

Hypothesis • • •

Hypotonic solution causes the plant cells to become turgid. Hypertonic solution causes the plant cells to undergo plasmolysis. Isotonic solution causes the plant cells to become flaccid.

Variables Manipulated: Concentration of surrounding solution Responding: Plant cells condition Fixed: Types of plant cells

sucrose solution

filter paper

Materials 0.50 M and 1.0 M sucrose solutions, distilled water, filter paper and an onion bulb

Apparatus Light microscope, glass slide, cover slip, small knife, mounting needle, dropper and a pair of forceps

Procedure 1 Prepare three slides and label as A, B and C. 2 Peel off the epidermal layer (skin) from the inner surface of an onion scale leaf and place it in a drop of distilled water on slide A. Use a cover slip to cover the glass slide. 3 Observe the epidermal cells of the onion scale leaf under the microscope. Draw and label your observation. 4 Peel off another epidermal layer (skin) of the onion scale leaf and put it on slide B. Cover with a cover slip. Add a drop of 0.50 M sucrose solution on the edge of one side of the cover slip. Spread the solution under the cover slip by placing a filter paper at the opposite side of the cover slip. Examine the epidermal cell under the microscope. Draw and label your observation. 5 Repeat step 4 by replacing 0.50 M sucrose solution with 1.0 M sucrose solution (slide C). 6 Flow excess distilled water through the onion scale leaf on slide C. Observe the cells under the microscope. Draw and label your observation.

Results Slide

Observation

Labelled drawing of cell shape

A (distilled water) B (0.5 M sucrose solution) C (1.0 M sucrose solution) Slide C after being flowed with excess distilled water

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Discussion 1 Discuss and explain the results obtained for each slide. 2 Which solution is hypotonic, hypertonic and isotonic to plant cells? 3 What happened to the plant cells in slide C?

Conclusion

Activity 1.2

3.5

CHAPTER 3

Is the hypothesis accepted? Suggest a suitable conclusion.

Studying and determining the concentration of extracellular solution which is isotonic to the cell sap of a plant

Experiment

Problem statement What is the concentration of the extracellular solution which is isotonic to the cell sap of potatoes?

Hypothesis Concentration of the extracellular solution which is isotonic to the potato cell sap does not change the mass of the potato cell sap.

Variables Manipulated: Concentration of sucrose solution Responding: Percentage of difference in the mass of potato strips Fixed: Soaking period, surrounding temperature and type of potato

Materials Potato, distilled water, 0.1 M, 0.2 M, 0.3 M, 0.4 M, 0.5 M, 0.6 M sucrose solutions and filter paper

Apparatus Test tube, cork borer, knife, forceps, ruler, 50 ml beaker, measuring cylinder, test tube rack and electronic weighing scale

Procedure 1 Seven petri dishes are prepared and labelled as A, B, C, D, E, F and G. 2 Fill each beaker with the following solutions: 3

Beaker A: distilled water Beaker E: 0.4 M sucrose solution Beaker B: 0.1 M sucrose solution Beaker F: 0.5 M sucrose solution Beaker C: 0.2 M sucrose solution Beaker G: 0.6 M sucrose solution Beaker D: 0.3 M sucrose solution A medium-sized cork borer is pressed into a potato.

4 The potato strip is then removed from the cork borer.

Take Note! Do not hold the potato with your hands while cutting. You should use a cutting board as a base.

5 Next, the potato strip is cut to 50 mm in length. 6 Steps 3 to 5 are repeated to obtain 6 more cylinder of potato strips of the same length. 7 Wipe the potato strips using filter paper and each is weighed to get the initial mass. 8 Pour the solutions in beaker A to G into the test tube A to G, respectively. Each potato strip is soaked completely in each test tube.

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9 After soaking for 30 minutes, remove each potato strip from the respective test tube and wipe dry with a filter paper. Weigh each strip to get the final mass. 10 The results are recorded. Plot a graph of the percentage of difference in mass against the concentration of sucrose solution.

Results

Test tube

Beaker

Mass of potato strips (g) Initial mass

A

Distilled water

B

0.1 M sucrose solution

Final mass

Difference in mass (g)

Percentage of difference in mass (%)

Discussion 1 What is the texture and condition of each potato strip after being soaked in different concentrations of sucrose solutions? 2 How do you determine the concentration of sucrose solution which is isotonic to the potato sap cell from your graph? 3 Based on the experiment, discuss the process of osmosis in different concentrations of sucrose solutions.

Conclusion Is the hypothesis accepted? Suggest a suitable conclusion.

Formative Practice

3.3

1 Explain what will happen to the following cells when they are soaked in a solution with a higher concentration of solutes compared to the intracellular fluid: (a) red blood cells (b) plant cells 2 Explain the effect of the hypotonic solution on red blood cells. 3 Explain the effect of the isotonic solution on plant cells. 4 Explain the following situations based on the osmosis concept: (a) Why do hawkers spray water on their fruits and vegetables? (b) Explain what happens when sugar is sprinkled on strawberries.

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You have definitely eaten canned pickles, salted fish and fruits before. How are the concepts of osmosis and diffusion applied in food preservation? You can also apply the concept of movement of substances across a plasma membrane by conducting Activity 3.6.

Activity ivitcA 1.2seit3.6

Applying the concept of movement of substances across a plasma membrane

CHAPTER 3

3.4

Movement of Substances Across a Plasma Membrane and Its Application in Daily Life

Project

Materials Egg, banana, cabbage, a variety of fruits, gelama fish, sugar, salt, vinegar and boiled water

Apparatus Knife, bottle and oven

Malaysian Innovation

Procedure

A group of researchers in Malaysia were successful in developing Sil-RH Membrane Distillation. This membrane is made from paddy chaff and can be used for the desalination process.

1 Conduct the activity in a group. 2 Apply the concept of movement of substances across a plasma membrane in food production. 3 Use local raw materials and market the products at schools. 4 Among the food products that you can prepare are colourful preserved eggs, different flavours of smoked banana, salted fish, pickles and coloured cabbage.

Phenomenon of plant wilting Fresh plants

Excessive use of fertilisers may cause wilting in plants. Dissolved fertilisers will cause soil water to be hypertonic to the sap cell of roots. Consequently, water will diffuse by osmosis from the roots’ cell sap to the soil, and cells will become plasmolysed. Cells in plants will recover once they are watered. However, if the period of plasmolysis is prolonged, wilted plants will eventually die.

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The concept of movement of substances across a plasma membrane has many applications in our daily lives, for example: Saline solutions, normally used in medicine, are isotonic solution to the blood plasma. It contains 0.85–0.90 g sodium chloride per 100 ml.

Rehydration drinks such as oral rehydration salts help to recover loss of water and electrolytes in individuals with diarrhoea.

water-insoluble drugs are transported in the hydrophobic area

Isotonic drinks help athletes to recover loss of water and electrolytes such as potassium and sodium through perspiration.

Reverse osmosis is a technology commonly used to extract fresh water from seawater using the desalination process. In a reverse osmosis equipment, pressure is applied to push the seawater through a semi-permeable membrane. The membrane allows water molecules to pass through it but not foreign particles, salt and microorganisms. As a result, only pure fresh water is released.

Activity Zone Study the reverse osmosis process in water purification.

water-soluble drugs are transported in the hydrophilic area

Liposomes are vesicles that contain aqueous solution surrounded by a phospholipid bilayer membrane. Liposomes are used to protect drugs or active substances taken orally from being destroyed by gastric juices. This way, drugs can reach the target cells.

pressure is applied

selectively permeable membrane

salt water goes in

Formative Practice

foreign particles and microorganisms

fresh water comes out water molecules

3.4

1 Explain why green chillies are preserved using vinegar and sugar. 2 Pickled pineapples are prepared by soaking the pineapple pieces in a thick sugar solution. State two advantages and disadvantages of this method as compared with keeping fresh pineapples. 3 Ariana had diarrhoea after eating stale food. Suggest something that can help her to recover.

ICT 3.4 Video: Liposome application (Accessed on 21 August 2019)

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4 A liposome is a vesicle that contains an aqueous solution that is surrounded by a phospholipid bilayer membrane. Explain the use of liposomes in everyday life. 3.4.3

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Summary MOVEMENT OF SUBSTANCES ACROSS A PLASMA MEMBRANE

Structure of Plasma Membrane

• Fluid mosaic model • Plasma membrane consists of carrier proteins, channel proteins, phospholipid bilayer, glycoprotein, glycolipid and cholesterol

Concept of Movement of Substances Across a Plasma Membrane

Movement of Substances Across a Plasma Membrane in Living Organisms

Movement of Substances Across a Plasma Membrane and its Application in Daily Life

• Passive transport – Simple diffusion – Osmosis – Facilitated diffusion

• Passive and active transport in living organisms • Isotonic, hypotonic and hypertonic solutions • Effect of isotonic, hypotonic and hypertonic solutions on animal cells and plant cells

• Phenomenon of plant wilting • Application of movement of substances across a plasma membrane in daily life • Reverse osmosis process in water purification

• Active transport

Self Reflection Have you mastered the following important concepts? • The necessit y of movement of substances across a plasma membrane • Components of a plasma membrane and its function based on the fluid mosaic model • Permeabilit y of a plasma membrane • The characteristics of substances that are able to move across a plasma membrane • Passive and active transport • Hypotonic, hypertonic and isotonic solutions • Effect of different solution concentrations on plant cells and animal cells • Application of the concept of movement of substances across a plasma membrane in daily life

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Summative Practice 3 1 State the meaning of passive transport. 2 The characteristic of a membrane decides if the molecule can move across the membrane. Explain why the plasma membrane is impermeable to many types of molecules. 3 Explain why food is preserved using a thick sugar solution. 4 (a) Explain the role of contractile vacuole in controlling the water equilibrum in an Amoeba sp. (b) Predict what will happen when the Amoeba sp. is transferred to the sea. Explain your answer. 5 (a) (b)

Figure 1 shows one component cell that is found in the cell. (i) Name the component of the cell in Figure 1. (ii) Label X and Y. In an experiment, the palisade mesophyll is soaked Y in filtered water for a period of time. Explain what Y: will happen to the cell.

Extracellular X X:

6 Figure 2 shows a type of substance movement across a plasma membrane. Explain why calcium ion in Figure 2 is taken to extracellular.

Intracellular FIGURE 1

Extracellular

ADP ATP site

Intracellular Ca2+ ATP

FIGURE 2

P

7 A research on the effect of the concentration of different salt solutions on human red blood cells was conducted. A droplet of blood was dropped into three test tubes A, B and C containing different solution contents. Test tube A contained 4.5% sodium chloride, test tube B contained filtered water and test tube C contained 0.85% sodium chloride. All three test tubes were set aside for 30 minutes. (a) Explain the observed solution of each test tube for 30 minutes. (b) Describe your observation on test tubes A and B. (c) Draw the shape of the red blood cell for each test tube when viewed through the microscope. (d) Suggest a suitable concentrated solution to keep red blood cells. Give justifications for your answer.

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Essay Questions 8 State the similarities and differences between simple diffusion and osmosis. 9 (a) Some housewives soak their vegetables in salt solution before cooking to get rid of pesticides and worms. (i) Explain why vegetables that are soaked too long in salt solution wither. (ii) Suggest a way to revive the turgidity of the vegetables. (b) Explain in detail how the molecules of amino acid are moved across a plasma membrane. (c) Cosmetic cream containing lyposome is said to be more effective in skin care. Give your assessment on this statement. Enrichment 10 You work in a company that produces drinks for different groups of athletes. The suggested carbohydrate concentration for the drinks are as follows: A gymnast:1–3%; middle distance runner: 6–8%; and footballer:10–12%. Give justifications for the concentration of drinks that you produce. 11 The rate of movement of material P and material S across a plasma membrane is shown in Figure 3 and 4. (a) Give an example of material P and explain how material P can move across a membrane plasma. (b) Compare the movements of material P and material S across the membrane plasma. Rate of movement of P (mg s–1)

Movement rate of S (mg s–1)

0.4

Movement rate of S (unit s-1)

Rate of movement of P (unit s-1)

1

10–1

PP

10–2

10–3

10–4

0

5

10

Concentration of material P (unit)

Concentration of material P (unit) FIGURE 3

0.3

0.2

SS

0.1

10–4

0

5

10

Concentration of material S (unit)

Concentration of material S (unit) FIGURE 4

Complete answers are available by scanning the QR code provided

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4

CHAPTER

Chemical Composition in a Cell

How can the knowledge of biological elements and molecules be used for biological control of fresh water snails?

• • •

• •

Do You KNOW…

What is the chemica l composition in a cell? What are the proper ties of water and its importance in a cell? What are the elemen ts found in carbohydrates, prot eins, lipids and nucleic acids? How are polymers produced from monomers? What is the importa nce of carbohydrates, prot eins, lipids and nucleic acids in a cell?

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4.1 Water 4.1.1 Describe the properties of water molecule. 4.1.2 Correlate the properties of water with its importance in the cell. 4.2 Carbohydrates 4.2.1 List the elements of carbohydrate. 4.2.2 Explain the types of carbohydrates: • monosaccharides. • disaccharides. • polysaccharides. 4.2.3 Conceptualise the formation and breakdown of: • disaccharides. • polysaccharides. 4.2.4 Write and explain the word equation for the formation and the breakdown of disaccharides. 4.2.5 Justify the importance of carbohydrates in cell. 4.3 Proteins 4.3.1 List the elements of proteins. 4.3.2 Conceptualise the formation and breakdown of dipeptides and polypeptides. 4.3.3 Write and explain the word equation for the formation and the breakdown of dipeptides. 4.3.4 Justify the importance of proteins in a cell.

4.4 Lipids 4.4.1 List the elements in lipids. 4.4.2 Explain the main types of lipids. 4.4.3 Describe the formation and the breakdown of a triglyceride. 4.4.4 Write and explain the word equation for the formation and the breakdown of a triglyceride. 4.4.5 Justify the importance of lipids in cell and multicellular organisms. 4.5 Nucleic acids 4.5.1 List the elements in nucleic acids. 4.5.2 Explain the structure of nucleotides: • nitrogenous base • ribose or deoxyribose sugars • phosphate 4.5.3 Describe the structure of the nucleic acids: • deoxyribonucleic acid (DNA) • ribonucleic acid (RNA) 4.5.4 Justify the importance of nucleic acids in cells: • carrier of hereditary information. • production of proteins. 4.5.5 Describe the formation of chromosomes from DNA and proteins.

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4.1

Water In Form Two, you have learned briefly about water and organic compounds. Examples of organic compounds are carbohydrates, proteins, lipids and nucleic acids. What is the function of organic compounds and water in the cells of an organism?

Properties of water and its importance in a cell POLARITY OF WATER

O H

H

H

O H

hydrogen bond FIGURE 4.1 Hydrogen bond between water molecules

• Water is an inorganic compound consisting of the hydrogen (H) and oxygen (O) elements. • Water molecules are polar molecules because shared electrons between oxygen and hydrogen will be attracted towards oxygen which is more electronegative (δ–). • This polarity produces hydrogen bonds and allows water to act as a universal solvent (Figure 4.1). • The universal solvent properties of water allow solutes such as glucose and electrolytes to be transported through the plasma membranes into cells for biochemical reactions.

COHESIVE FORCE AND ADHESIVE FORCE OF WATER

xylem vessel cohesive force adhesive force

• Water molecules are attached to each other through a cohesive force. • At the same time, water molecules are also attached to other surfaces through adhesive force. • Both forces produce the capillary action which allows water to enter and move along narrow spaces, such as in the xylem tube.

FIGURE 4.2 Cohesive force and adhesive force inside the xylem tube

SPECIFIC HEAT CAPACITY OF WATER

Brainstorm! How do aquatic animals live in frozen sea water?

water

PHOTOGRAPH 4.1 A polar bear in the sea covered with ice

• • •

Water has a high specific heat capacity of 4.2 kJ kg-1 °C-1. This means that 4.2 kJ of heat energy is required to raise the temperature of one kilogram of water by 1°C. Water absorbs a lot of heat energy with a small rise in temperature. This characteristic is very important to maintain the body temperature of organisms.

Formative Practice

4.1

ICT 4.1

1 What chemical bonds are broken when water changes from liquid to water vapour?

Quiz: Test your understanding of water

2 Why is water known as polar molecule?

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3 State the meaning of adhesive force and cohesive force. 4 Explain how perspiration helps to lower the body temperature.

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Organic compounds are chemical compounds that contain carbon elements. Large and complex compounds form macromolecules. Most macromolecules are polymers comprising small molecules known as monomers (building blocks). Carbohydrates, proteins and nucleic acids are polymer molecules of organic compounds. Carbohydrates are important as a source of energy and the basic structure of some organisms. Carbohydrates are organic compounds consisting of the elements carbon (C), hydrogen (H) and oxygen (O) in the ratio 1:2:1 and with the chemical formula (CH2O)n.

CHAPTER 4

4.2

Carbohydrates

Types of carbohydrates There are three main types of carbohydrates, which are: • monosaccharides (simple sugars) • disaccharides • polysaccharides (complex sugars) PHOTOGRAPH 4.2 Foods rich in carbohydrates

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Monosaccharides Monosaccharides are carbohydrate monomers, which are the simplest carbohydrate units. Monosaccharides can combine to form polymers through a condensation reaction. Most monosaccharides taste sweet, can form crystals and dissolve in water. Examples of monosaccharides: • Glucose is a sugar found in plants such as rice and wheat as well as fruits such as grapes. Glucose is the most commonly found monosaccharide and most polysaccharides are formed from this sugar. • Fructose is the sugar found in honey and sweet fruits. • Galactose is found in milk. Monosaccharide has the reducing power, which is the ability to transfer hydrogen (or electron) to other compounds. This is called the reducing process. When the monosaccharide is heated in Benedict’s solution, the monosaccharide will reduce the blue copper (II) sulphate to a brick red precipitate of copper (I) oxide which is not soluble in water. All monosaccharides give this reaction and it is known as reducing sugars.

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Activity Zone Design an experiment to ascertain the presence of reducing sugar and nonreducing sugar (sucrose).

Disaccharides Disaccharide molecules are formed when two simple sugar molecules (monosaccharides) combine through condensation to form a disaccharide unit. This process involves the removal of a water molecule. condensation

Glucose + glucose

condensation

Glucose + fructose Glucose + galactose

condensation

Maltose + water Sucrose + water Lactose + water

Disaccharides can also be broken down to their monosaccharide units through hydrolysis and the addition of one water molecule. Maltose + water

Sucrose + water Lactose + water

hydrolysis hydrolysis hydrolysis

Glucose + glucose Glucose + fructose Glucose + galactose

Examples of disaccharides include sucrose, maltose and lactose (Photograph 4.3). Lactose and maltose are reducing sugars while sucrose is a non-reducing sugar.

Maltose is found in grains

Lactose in milk

Biological Lens Sucrose is a nonreducing sugar because it does not reduce copper (II) sulphate solution. If sucrose is hydrolysed (disintegrated) into units of monosaccharides (glucose and fructose) earlier, the Benedict’s test will show a positive result.

Sucrose is found in sugar cane, sweet fruits and sugar beet PHOTOGRAPH 4.3 Examples of disaccharides and its sources

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Polysaccharides

ICT 4.2 TMK 4.2 Quiz: Test your understanding of carbohydrates

CHAPTER 4

Polysaccharides are sugar polymers consisting of monosaccharide monomers. Similar to disaccharides, polysaccharides are formed through the condensation process and involves hundreds of monosaccharides to form long molecular chains. Polysaccharides are not soluble in water due to their large molecular size. Polysaccharides neither taste sweet nor crystallise. Polysaccharides can also disintegrate through hydrolysis with the help of dilute acids, boiling and enzyme action. Polysaccharides play various roles in organisms.

Importance of carbohydrates in cells • • •

As a source of energy, for example glucose As a food reserve, for example glycogen in animal cells and starch in plant cells As a support structure, for example cellulose in the plant cell wall Cellulose forms the main structure of the plant cell wall. Starch is the main storage of polysaccharide in plants. Starch is also found in chloroplasts. Source: grains, potatoes and legumes.

plant cell wall

Glycogen is the main storage of polysaccharide found in muscle cells and animal liver cells.

PHOTOGRAPH 4.4 Examples of polysaccharides

Our World of Biology Formative Practice

4.2

1 Name the elements in carbohydrates. 2 List the main types of carbohydrates. 3 Give examples of reducing sugars and non-reducing sugars.

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4 Explain why sucrose is a non-reducing sugar.

Chitin, a type of polysaccharide, is used as a surgical thread. The advantage is that chitin will decompose after the sewn wound heals.

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4.3

Protein Protein is a complex compound composed of carbon, hydrogen, oxygen and nitrogen elements. Most proteins also contain sulphur and phosphorus. Foods rich in proteins include fish, meat, milk, beans and eggs. All proteins are composed of one or more polymers known as polypeptides. Each polypeptide is made up of monomers or small units known as amino acids. A polypeptide can consist of fifty to thousands of amino acid molecules. Amino acids are linked together through the condensation process. Dipeptides are composed of two amino acid molecules which are linked together by a peptide bond through the condensation process. In this process, one water molecule is removed. Further condensation can link more amino acids to form a polypeptide chain.

Amino acid + amino acid Dipeptide + water PHOTOGRAPH 4.5 Foods rich in proteins

condensation

hydrolysis

Dipeptide + water

Amino acid + amino acid

Each dipeptide can be broken down into an amino acid through hydrolysis. There are about 20 types of amino acids present naturally. Various types of polypeptide molecules can be formed from the 20 types of amino acids. This is because each type of protein differs in terms of the amino acid sequence in its polypeptide chain.

Importance of proteins in a cell

ICT 4.3 Quiz: Test your understanding of proteins

Proteins are used to build new cells, repair damaged tissues and for the synthesis of enzymes, hormones, antibodies and haemoglobin. Proteins also form building blocks such as keratin in the skin, collagen in bones and myosin in muscle tissues. The breakdown of proteins or polypeptides by digestive enzymes gives us the energy to carry out our daily activities. Polypeptides can disintegrate into amino acids. This amino acid is then used again to build the protein molecules needed by the body. You will learn in detail about the process of protein digestion in Chapter 9. Formative Practice

4.3

1 State the monomers of proteins. 2 Name the reaction that forms dipeptide.

4 Explain the effect of protein deficiency in a diet on the hair and nails of an individual.

3 State two importance of proteins.

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4.3.1

4.3.2

4.3.3

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Biological Lens The presence of fats can be tested with the ethanol emulsion test. The formation of a white emulsion shows a positive result of the presence of lipids.

Lipids are naturally occurring hydrophobic compounds found in plant and animal tissues. Like carbohydrates, lipid is made up of carbon, hydrogen and oxygen elements but with a much higher ratio of hydrogen atoms to oxygen atoms. Lipids are insoluble in water but soluble in other organic solvents, for example, alcohol, ether and chloroform. CHAPTER 4

4.4

Lipids

Types of lipids Types of lipids include fats, waxes, phospholipids and steroids.

Fats Fats and oils are triglycerides. Triglycerides are a type of ester formed from the condensation of one glycerol molecule with three molecules of fatty acids. Triglycerides can be hydrolysed again into fatty acids and glycerol through the reaction of hydrolysis. Glycerols are a type of three carbon alcohol that contain three hydroxyl groups (–OH).

ICT 4.4

condensation

Quiz: Test your understanding of lipids

+ glycerol

+ hydrolysis fatty acids

triglycerides

3H2O water

There are two types of fatty acids, namely saturated fatty acids and unsaturated fatty acids. The similarities and differences between saturated fats and unsaturated fats are shown in Tables 4.1 and 4.2. TABLE 4.1 Similarities between saturated fats and unsaturated fats

Similarities PHOTOGRAPH 4.6 Foods rich in lipids

Both consist of carbon, hydrogen and oxygen elements. Both contain glycerol and fatty acids. Both contain nonpolar molecules.

4.4.1

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4.4.3

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TABLE 4.2 Comparison between saturated fats and fatsH H H H H H Hunsaturated O=

H–O –

Saturated fats Fatty acids only have single bonds between carbon. O=

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H C– C– C– – H C H C– H O= C– H H –O H

H

H H H H Do not form chemicalHbonds with H additional = C– H H C C– – H Hbecause C C – between hydrogen atoms all bonds – H H C C– H – H H C C– H – H H H C– C carbon atoms are saturated. – H H C– –C H

C O= C– H H O –

H

H

H



Exist in solid form at room temperature. H

H

Saturated fats are not good for health because it raises the cholesterol level in the blood in the form of low-density lipoprotein (LDL). This increases the risk of a heart attack. Saturated fats can also increase the risk of diabetes.

H

H

H

H

H

H

H

H

H

H

H

C–

H

H H H = C– H C– H C– H C– H H C– H H H C– H C– H C– H H double H H

H

C C–

bond

Double bonds can still receive one or more additional hydrogen atoms because carbon atoms are unsaturated. H

Source: butter and animal fat

Our World of Biology

H

Fatty acids have at least one double bond between carbon.

C – C – C – C – C – C – C – C – C – C– C – C – C – C – C – C – H H

H

Unsaturated H H H H H H H H fats

H

H



H–O –

H

H

C – C – C – C – C – C – C – C – C – C– C – C – C – C – C – C – H

Exist in liquid form at room temperature. Source: olive and fish oil

Wax Wax contains one molecule of alcohol that combines with another molecule of fatty acid and is waterproof.

Phospholipid Phospholipids are a major component of plasma membranes and are made up of one molecule of glycerol that combines with two molecules of fatty acid and one group of phosphate.

Steroids Steroids are lipids that do not contain fatty acids. Examples of steroids are cholesterol, testosterone, estrogen and progesterone.

Importance of lipids in cells Fats function as reserved energy for animals. In addition, fats also function as a liner to protect internal organs and act as a heat insulator for animals. Waxes are an important component in cuticles that cover the epidermis of leaves and sebum secreted by our skin. The function of glycolipid is to ensure the stability of the plasma membrane and to help in the cell identification process. Cholesterol is important in steroid hormone synthesis.

Formative Practice

4.4

1 State the elements in lipids. 2 List the types of lipids.

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3 Give your opinion on the intake of synthetic steroids to build body muscles. 4.4.4

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4.5

Nucleic acids are one or two polymer chains comprising of nucleotide monomers. Nucleic acids are formed from the elements of carbon, hydrogen, oxygen, nitrogen and phosphorus. Each nucleotide consists of a pentose sugar (5-carbon sugar), a nitrogenous base and a phosphate group that are combined together through the condensation process (Figure 4.3). There are two types of pentose sugars, that are, ribose and deoxyribose. The nitrogenous base consists of adenine (A) guanine (G), cytosine (C), thymine (T) and uracil (U).

ICT 4.5

There are two types of nucleic acids: • deoxyribonucleic acid (DNA) • ribonucleic acid (RNA) Ribonucleic acid (RNA) contains ribose sugar while deoxyribonucleic acid (DNA) contains deoxyribose sugar.

Activity: Making a DNA model

CHAPTER 4

Nucleic Acids

Deoxyribonucleic acid (DNA) DNA consists of two polynucleotide chains that are intertwined in opposite directions and form the double helix (Figure 4.3). The nitrogenous base groups on both polynucleotide chains are matched and bound together by hydrogen bonds. The nitrogenous bases for DNA are adenine (A), guanine (G), thymine (T) and cytosine (C). Adenine will pair with thymine while guanine will pair with cytosine.

double helix structure of DNA double helix structure of DNA

T

T

A hydrogen bonds between nitrogenous base C G

gen between enous base

C G sugar-phosphate chain

nucleotide T A

A

T

T

A C

T

A C

sugar-phosphate chain

A

nitrogen

phosphate group

nitrogenous base

phosphate group

deoxyribose sugar

G deoxyribose sugar

G

FIGURE 4.3 Double helix structure of DNA 4.5.1

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Adenina N HRNA 2N structureH The is a single polynucleotide chain which is shorter Ribonucleic acid (RNA)

compared to DNA (Figure 4.4). N The nitrogenous N bases for RNA are adenine, guanine, cytosine and uracil. Thymine in H N DNA is replaced by uracil in RNA. The three main types of RNA, are messenger RNA (mRNA), ribosomal RNA (rRNA) and transfer RNA (tRNA). These three RNAs are involved in the protein synthesis process. Guanina

sugar and phosphate backbone

N O H Importance of nucleic acids in a cell H-N Ndetermines the characteristics of an organism such Do you know what as eye colourNor height? DNA is important as a carrier of hereditary NH

nitrogenous base

2 and a determinant of characteristics in living organisms. information DNA contains genetic codes carried by nitrogenous bases (A, G, C and T) for the synthesis of polypeptides which form proteins. Sitosina The genetic code is written as a series of three bases that determine the sequence acids in proteins to be synthesised. For example, the H of amino NH 2 AUG codon (base sequence: adenine, uracil and guanine) on mRNA H code forNmethionine amino acid (Figure 4.5). The three-base is the sequence DNA is transcribed into mRNA codons which are then N in O translated into the amino acid sequence to form a single polypeptide chain. This means that the sequence of nucleotides in DNA determines the aminoUrasil acid sequence in the polypeptide chain that builds the corresponding protein.

H

H FIGURE 4.4 Structure of RNA

DNA

RNA

O

DNA

N-H

transcription

N O codons

A U G C GA UA C

mRNA

translation Polypeptides methionine arginine tyrosine FIGURE 4.5 Genetic code on mRNA is translated into protein ICT 4.6 Quiz: Test your understanding of nucleic acids

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Formation of chromosomes from DNA and proteins Chromosomes are formed from DNA polynucleotide chains that are wound around a protein called histone. Histones do not carry genetic information. DNA molecules combine with histone proteins to form nucleosomes. Nucleosomes are intertwined to form the chromosome structure. 4.5.3

4.5.4

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DNA nitrogenous base pairs adenine (A) thymine (T) guanine (G) cytosine (C)

HISTONE gene

NUCLEOSOME

CHROMOSOME

AR

CHAPTER 4

CELL nucleus

FIGURE 4.6 Formation of chromosome from DNA and proteins

Formative Practice

4.5

1 State two types of nucleic acids. 2 State the components in a nucleotide.

3 Explain why the RNA structure is shorter than the DNA structure. 4 Explain the possibility that may occur if a cell does not have a nucleic acid.

Summary CHEMICAL COMPOSTION IN A CELL

Water

Carbohydrates

Proteins

Lipids

Characteristics: water polarity, specific heat capacity of water, adhesive force and cohesive force of water

Type: • monosaccharide: glucose, fructose and galactose • disaccharide: maltose, sucrose and lactose • polysaccharide: starch, glycogen and cellulose

Amino acid

• Type: fats, wax, phospholipids and steroids • Comparison between saturated fats and unsaturated fats

Dipeptides

Polypeptides

Nucleic Acids • Each nucleotide consists of pentose sugar, nitrogeneous base and phosphat group • Type: -- DNA -- RNA

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Self Reflection Have you mastered the following important concepts? • Properties of water and its importance in cells • Types of carbohydrates and its importance in cells • Elements of proteins and its importance in cells

• Types of lipids and its importance in cells • Structure of nucleic acids and its importance in cells • Formation of chromosomes

Summative Practice 4 1 Wax is a type of lipid. Wax can be found in the leaf cuticle, fruits and seeds. Explain the function of wax on a fruit skin. 2 Figure 1 shows a nucleotide. (a) Name the components P, Q and R. (b) Complete Figure 2 to show a complete DNA molecule.

P R

FIGURE 1

Q

FIGURE 2

3 State the differences between (a) the structure of a DNA molecule and a polypeptide molecule (b) the structure of DNA and RNA

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4 (a) How does water help in the respiration and digestion process? (b) What are the characteristics of aquatic life that allows them to live throughout winter? 5 Figure 3 shows the reaction between the formation and the decomposition of lipids. (a) (i) Name the parts labelled K, L and M. (ii) State processes P and Q. P (b) Fatty acids are divided into saturated fatty acids and unsaturated fatty acids. State the four differences between saturated fats and unsaturated fats. Essay Questions

+

+ H2O Q

K

M

L FIGURE 3

6 Figure 4 shows the production of carbohydrates through the process of photosynthesis. Carbohydrate is a type of macromolecule. (a) Explain the meaning of organic compound macromolecules. (b) Explain the formation of polysaccharide. (c) Discuss the importance of organic compounds in sunlight cells. oxygen Enrichment 7 Ariff practises a diet low in carbohydrates. Suggest carbon what needs to be done to reduce the starch in potatoes dioxide during food preparation.

water

8 The results of biological studies have been widely applied in various industries to enhance quality and FIGURE 4 productivity and to overcome problems. Among the studies being used by environmentalists are biodegradable plastics and environmentally friendly batteries. A group of scientists in Malaysia have succeeded in inventing environmentally friendly batteries using seaweed pulp. In your opinion, how did research on chemical elements in seaweed help scientists to invent environmentally friendly products?

Complete answers are available by scanning the QR code provided

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5

CHAPTER

Metabolism and Enzymes



What is the purpose of the enzyme extracted from fungi?

Do you KNOW...

What types of metab olism occur in a cell? • What are the ch aracteristics of the enzyme and its mechanism of action? • What are the fa ctors that influence the reactio n of enzymes? • What is the ap plication of enzymes on everyd ay life?

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5.1 Metabolism 5.1.1 Define metabolism. 5.1.2 State the types of metabolism in a cell: • anabolism • catabolism 5.2 Enzymes 5.2.1 Define enzymes. 5.2.2 Reason out the necessity of enzymes in metabolism. 5.2.3 Describe the naming of enzymes with the addition of –ase to their substrates. 5.2.4 Characterise the general properties of enzymes. 5.2.5 Communicate about the involvement of specific organelles in the production of: • intracellular enzymes • extracellular enzymes 5.2.6 Explain the mechanism of enzyme action using the ‘lock and key’ hypothesis. 5.2.7 Interpret energy diagrams to explain the mechanism of enzyme action. 5.2.8 Correlate the mechanism of enzyme action with the change in the following factors: • temperature • pH • substrate concentration • enzyme concentration 5.2.9 Design and conduct experiments to study the effects of temperature and pH on the activities of amylase and pepsin. 5.3 Application of Enzymes in Daily Life 5.3.1 Explain by using examples the application of enzymes in daily life.

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5.1

Metabolism Metabolism refers to all chemical reactions that occur in a living organism. The processes in metabolism involve the conversion of food into energy in the form of ATP, and the formation of carbohydrate, protein, lipid and nucleic acid.

Types of metabolism in a cell There are two types of metabolism, which are catabolism and anabolism. Catabolism is the process of breaking down complex substances into simple substances. This reaction releases energy. For example, the breakdown of glucose during cellular respiration to generate energy. Generally, catabolic reactions are as follows:

A

(substrate)

B+C

(products)

Anabolism is the process of synthesising complex molecules from simple molecules. This reaction uses or absorbs energy. For example, the formation of glucose during photosynthesis. Generally, anabolic reactions are as follows:

A+B

(substrate)

5.2 Biological Lens The Alcanivorax borkumensis bacteria produces hydroxylase enzymes to break down an oil spill in the sea and change it to a non-toxic substance. substrate

C

(product)

Enzyme In a cell, biochemical reactions occur at a high rate to protect the living processes. Biochemical reactions can occur quickly in cells due to the presence of enzymes that help speed up reactions. An enzyme is an organic catalyst that is mostly made up of proteins and is produced by living cell organisms. However, not all enzymes products are synthesised from proteins. The substances needed for an enzyme reaction are called substrates. Substrates will bind with enzymes at a specific site known as the active site and form an enzyme-substrate complex (Figure 5.1). H2O H2O H2O active site

substrate enzyme

products

active site active site

substrate enzyme-substrate enzyme enzyme complex

enzyme-substrate enzyme-substrate complex complex

FIGURE 5.1 Formation of an enzyme-substrate complex

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5.1.1

5.1.2

5.2.1 5.1.1

5.2.2 5.1.2

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en

Enzyme nomenclature

Activity Zone

In the 1960s, The International Union of Biochemistry and Molecular Biology (IUBMB) introduced the enzyme nomenclature based on the substrate or reaction it catalyses. The name of the enzyme is derived by adding ‘-ase’ to the name of the substrate it catalyses. An example of the ‘-ase’ added to substrate is the lactase enzyme, which catalyses the hydrolysis of lactose. Lactose + water

Lactase

Glucose + galactose

Collect information on the enzyme nomenclature conventionally and based on The International Union of Biochemistry and Molecular Biology (IUBMB). Present it in class.

CHAPTER 5

However, there are also a few enzymes that do not follow this naming system, especially enzymes that were discovered before the systematic naming system was introduced. Some examples are: trypsin, pepsin, and renin.

General characteristics of enzymes

Enzymes act rapidly.





5.2.3

Enzymes are biological catalysts that speed up biochemical reactions.

Some enzymes need cofactors to work more efficiently. An example of a cofactor is vitamin B, and magnesium ion.

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Enzymes are only required in small quantities and are reusable.

The structure of enzymes remain unchanged and are not destroyed after a reaction.

The reaction of enzymes are specific. Only substrate that fit the form completely with an enzyme in an active site can combine.



Most of the reactions catalysed by enzymes are reversible.

GENERAL CHARACTERISTICS OF ENZYMES



Enzyme activity can be slowed down or stopped by enzyme inhibitors. An example of an inhibitor is heavy metal such as lead or mercury.

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Intracellular and extracellular enzymes

Biological Lens

Enzymes that are synthesised in a cell for its own use are called intracellular enzymes. For example, the hexokinase enzyme that is used in the glycolysis process during cellular respiration. On the other hand, enzymes that are secreted outside the cell are known as extracellular enzymes. For example, the trypsin enzyme is produced by the pancreatic cells and secreted into the duodenum to break down polypeptides. How are extracellular enzymes produced? The production of enzymes involves a few specific components of cells (Figure 5.2).

‘Glycolysis’ originates from the words ‘glucose’ and ‘lysis’ (break down) and is the breakdown of glucose by the hexokinase enzyme to produce energy and pyruvate.

1

2 Ribosome is the site of protein synthesis.

3 Once it reaches the end of the rough endoplasmic reticulum, the membrane buds off to form transport vesicles.

Proteins synthesised by ribosome enter the lumen of the rough endoplasmic reticulum and are transported through it.

nuclear membrane nucleus pore

6

rough endoplasmic reticulum

protein secreted as enzymes

plasma membrane 2 1

5

ribosome 3 secretory vesicle

smooth protein endoplasmic reticulum Golgi apparatus

4 transport vesicle

4

The transport vesicle that contains proteins moves towards the Golgi apparatus and then fuses with it.

5

In the Golgi apparatus, the proteins are modified into enzymes and secreted in secretory vesicles that are formed from the tip of the Golgi apparatus.

6

Secretory vesicles will move towards the plasma membrane and fuse with it to secrete extracellular enzymes.

FIGURE 5.2 Production of extracellular enzymes

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Mechanism of enzyme action The ‘lock and key’ hypothesis Most enzymes are complex proteins made up of polypeptide chains that are folded into three-dimensional structures. This three-dimensional structure has an active site with a specific configuration that complements a specific substrate molecule. The binding of a molecule substrate on an active site of enzymes is specific like a ‘lock and key’ combination (Figure 5.3). The enzyme is represented by a ‘lock’ and the substrate is represented by a ‘key’.

products products products

2 Substrate combines with the

CHAPTER 5

substrate substrate substrate

AR

active site to form enzymesubstrate complex.

enzyme enzyme enzyme enzyme 1 The specific substrate approaches the enzyme.

Enzyme Enzyme Enzyme substrate complex substrate complex substrate complex

enzyme enzyme enzyme place and a product is 3 A reaction takes

created. The product then leaves the active site after the reaction is complete.

FIGURE 5.3 The ‘lock and key’ hypothesis

Most reactions inside the cell require high activation energy. Activation energy is the energy needed to break the bond in the substrate molecule before reaction can occur. Enzymes function by lowering the activation energy (Figure 5.4). By doing so, the rate of biochemical reactions in the cell is accelerated. Indicator:

energy in system

activation energy without enzyme

reaction without enzyme



reaction with enzyme

activation energy with enzyme reactants

products enzyme reaction

5.2.6



5.2.6 5.2.7 5.2.7

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FIGURE 5.4 The presence of enzymes will reduce the activation energy of a reaction

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The mechanism of enzyme action and factor changes There are many factors that affect the mechanism of enzyme action. The chemical bond in enzymes can be easily transformed as a result of chemical changes and physical conditions. Among these factors are temperature, pH, enzyme concentration and substrate concentration.

Effects of temperature Figure 5.5 shows the effects of temperature on the rate of biochemical reaction controlled by enzymes. 1 • At a low temperature, the rate of reaction catalysed by

rate of reaction

2

optimum temperature

enzymes is low. •

When the temperature rises, the kinetic energy of the substrate molecules and enzymes also increases. This increases the frequency of effective collision between the substrate molecules and enzyme molecules.



The rate of reaction between enzymes and substrate molecules increases.



With every rise in temperature of 10°C, the rate of reaction controlled by the enzymes will double until it reaches the optimal temperature.

1

3

37°C 10

20

30

40

50 60 temperature (°C)

FIGURE 5.5 The effects of temperature on the reaction rate of an enzyme

2 At optimal temperature, the enzyme reaction is at its maximum. The optimal temperature for enzyme reactions in the human body is around 37°C.

3 • After reaching the optimal temperature, any further increase in temperature will reduce the enzyme activity rapidly until it stops at 60°C. •

At this temperature, the enzymes become denatured as the chemical bonds in the enzyme molecules break at extreme temperatures.



The enzymes are unable to retain the three-dimensional form. The active site of enzymes changes. The substrate does not complement the active site of enzymes.

rate of reaction

Effects of pH optimum pH for pepsin

optimum pH for salivary amylase and most enzymes in animal cells

optimum pH for trypsin

10 5 6 7 8 9 pH FIGURE 5.6 The effect of pH on the enzyme activities of pepsin, salivary amylase and trypsin 0 1

2

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3

4



The enzyme activity is influenced by the pH of the surrounding solution. Generally, all enzymes react most effectively at their optimal pH.



Most enzymes are most active in the range of between pH 6 and 8. For example, the salivary amylase works at pH 6.8.



However, there are some exceptions. For example, the pepsin enzymes in the stomach act at the optimal pH range of between 1.5 and 2.5. The trypsin enzyme in the duodenum, on the other hand, only works well in an alkaline medium, at a pH of around 8.5 (Figure 5.6). 5.2.8

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The change in pH value changes the charge (ion H+) of the active site of enzymes and the substrate surface. As a result, the enzymesubstrate complex cannot be formed.



When the pH of the environment returns to the optimum level, the charge on the active site will be restored. The enzyme will return to function as normal.



The extreme change in the pH value will break the structural chemistry bond and change the active site of enzymes. Denatured enzyme (Figure 5.7).

Molecule of a normal enzyme

maximum level 10

2

0.5

1

substrate concentration FIGURE 5.8 The effect of substrate concentration on the rate of enzyme reaction

The effect of enzyme concentration

2

3

1 • When substrate concentration increases, the



opportunity for an effective collision between the substrate and enzyme molecules also increases. The reaction rate continues to increase until it reaches the maximum level. The rate of reaction is constant.

2 • At the maximum level, the concentration of

0

1

If the concentration of enzymes is fixed while the concentration of substrate is increased, the reaction rate controlled by enzymes will also increase, leading to an increase in products created (Figure 5.8).

CHAPTER 5

FIGURE 5.7 Molecule of a denatured enzyme

The effect of substrate concentration rate of reaction

Molecule of a denatured enzyme

When the concentration of enzyme increases, the rate of enzyme reaction will increase because of the presence of more active sites that are ready for catalytic action. If the concentration of an enzyme in one reaction is doubled, the amount of substrate converted to products per unit of time is also doubled with the condition that there is an excess supply of substrate. At the maximum rate, the concentration of the substrate becomes the limiting factor. The rate of reaction can only be increased by adding more substrate. 5.2.8

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enzymes becomes a limiting factor. The reaction rate can only increase when the concentration in enzymes increases. •

After reaching the maximum level, all active sites of enzymes are saturated with substrate and are involved in the catalytic reaction.

rate of reaction maximum level

1

2

3 enzyme concentration

FIGURE 5.9 Effects of enzyme concentration on the enzyme reaction rate

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Activity itcA 1.2seitiv5.1

Studying the effect of temperature on the amylase enzyme activity

Experiment

Problem statement What is the effect of temperature on the reaction rate of an amylase enzyme?

Hypothesis An increase in temperature increases the reaction rate of an amylase enzyme up to an optimum temperature. The reaction rate of an enzyme decreases after the optimum temperature.

Variables Manipulated: Temperature Responding: Reaction rate of an amylase enzyme Fixed: The concentration of amylase and starch suspension (substrate) and the pH of the reaction medium

Materials 1% starch suspension, 0.5% amylase enzyme solution, iodine solution, ice and filtered water

Apparatus Beaker, test tube, syringe, dropper, glass rod, white grooved tile, thermometer, Bunsen burner, tripod stand, wire gauze, test tube rack, measuring cylinder and stopwatch

Procedure 1 Using a syringe, put 5 ml of 1% starch suspension into each test tube labelled A1, B1, C1, D1 and E1. 2 Using another syringe, put 2 ml amylase enzyme solution in each test tube labelled A2, B2, C2, D2 and E2. 3 Test tubes A1 and A2, B1 and B2, C1 and C2, D1 and D2, E1 and E2, are placed respectively in 5 separate water baths at fixed temperatures of 20°C, 30°C, 40°C, 50°C and 60°C. 4 Incubate all test tubes for 5 minutes. 5 Meanwhile, prepare a dry, white grooved tile and put a drop of iodine solution into the tile. 6 After incubating for 5 minutes, pour the starch suspension in test tube A1 into test tube A2. Stir the mixture with a glass rod. Start the stopwatch immediately. 7 Use the dropper to extract a drop of the mixture from test tube A2 and drop it immediately into the first groove on the tile containing the iodine solution (The first groove is considered as zero minute). 8 Repeat the iodine test every 30 minutes. Rinse the dropper with the water from the beaker after each sampling. Record the time taken to complete the starch hydrolysis, that is, the time when the mixture remains brownish yellow in colour when tested with the iodine solution.

water bath at respective temperatures

9 Keep all test tubes immersed in the respective water baths throughout the experiment. Repeat steps 5 to 8 for each pair of test tubes B1/B2, C1/C2, D1/D2 and E1/E2. 5 ml starch 2 ml suspension amylase solution

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10 Record your results in an appropriate table. Plot your graph to show the reaction rate of the enzyme (minute-1) against temperature (°C).

Results Temperature (°C)

Time for starch hydrolysis to complete (minute)

Rate of reaction (minute-1)

20 30 40 CHAPTER 5

50 60

Discussion 1 Why do you need to incubate the test tubes in the respective water baths for 5 minutes at the beginning of the experiment? 2 What is the result of amylase action on starch? 3 What is the function of the iodine solution? 4 Based on the drawn graph, explain the effect of temperature on the enzyme activity.

Conclusion Is the hypothesis accepted? Suggest a suitable conclusion for this experiment.

Activity vitcA 1.2seiti5.2

Studying the effect of pH on the pepsin enzyme activity

Experiment

Problem statement What is the optimum pH of a pepsin enzyme reaction?

Hypothesis pH 2 is the most optimum for the pepsin enzyme reaction.

Variables Manipulated: pH medium reaction Responding: The clarity or turbidity of the mixture reaction Fixed: Albumen concentration, pepsin solution concentration and temperature of reaction medium

Materials Albumen suspension (egg white), 1% pepsin solution, 0.1 M hydrochloric acid, 0.1 M sodium hydroxide solution, water bath at the temperature of 37°C, pH paper and distilled water

Apparatus Beaker, dropper, thermometer, test tube, 5 ml syringe (without needle), stopwatch, Bunsen burner, tripod stand, wire gauze, thermometer and test tube rack

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Procedure 1 Prepare three test tubes and label as P, Q and R. 2 Put 5 ml albumen suspension in each test tube using a syringe.

P

Q

thermometer

R

3 Add the following solution into each test tube:

test tube

• P: 1 ml 0.1 M hydrochloric acid + 1 ml 1% pepsin solution • Q: 1 ml distilled water + 1 ml 1% pepsin solution • R: 1 ml 0.1 M sodium hydroxide solution + 1 ml 1% pepsin solution 4 Dip a piece of pH paper into each test tube and record the pH of the mixture.

water bath 37°C

5 Put all the test tubes in a water bath with a fixed temperature of 37°C for 20 minutes. 6 Observe the state of the mixture at the beginning of the experiment and after 20 minutes. 7 Record the results in a table.

Results Test tube

pH

Clarity or turbidity 0 minute

After 20 minutes

P Q R

Discussion 1 Why is it necessary to incubate the test tube in a water bath with a fixed temperature of 37°C? 2 What is the effect of pH on pepsin action on albumen? 3 Discuss the result obtained for test tubes P, Q and R.

Conclusion Is the hypothesis accepted? Suggest a suitable conclusion for this experiment.

Formative Practice

5.1

1 What will happen if ribosomes in a pancreas cell do not function? 2 Why must our body temperature be maintained at 37°C? 3 What is the optimum pH for a pepsin enzyme action? 4 Y is the enzyme that catalyses the hydrolysis of sucrose into glucose and fructose. What is enzyme Y?

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Enzymes have long been widely used in the commercial sector and for everyday use. The enzymes used are extracted from natural resources such as bacteria or are produced synthetically. Immobilized enzymes are enzymes that combine with inert and insoluble substances to increase the resistance of enzymes towards change in factors such as pH and temperature. With this method, the enzyme molecules will remain in the same position throughout the catalytic reaction and then be separated easily from its product. This technology is known as immobilized enzyme technology. This technology is used in various industrial applications (Photograph 5.1). Formative Practice

CHAPTER 5

5.3

Application of Enzymes in Daily Life

5.2

1 How are enzymes produced? 2 How does immobilized enzyme technology help to accelerate the enzyme reaction? 3 Give examples of industries that use enzymes in the manufacturing of products. Digestive enzymes are used in the medical sector Pectinase and cellulase enzymes are used in juice production

Amylase, lipase, protease and cellulase enzymes in bio detergent

Lactose enzymes are used in lactose-free milk

Trypsin enzyme extracts fur from animal hide to make leather products

Protease enzyme separates the fish skin

PHOTOGRAPH 5.1 Enzyme immobilization technology is used in various industrial application 5.3.1

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Summary METABOLISM AND ENZYMES

Metabolism • Anabolism • Catabolism

Enzyme • Enzyme nomenclature: adding -ase to the substrate • General characteristics of enzymes • Intracellular and extracellular enzymes • Enzyme action mechanism—‘lock and key’ hypothesis • Factors that influence the enzyme action – Temperature – pH – Substrate concentration – Enzyme concentration

Application of Enzymes in Daily Life • Digestive enzymes • Lactose-free milk and fruit juice • Bio detergent • Leather product (separate fur from animal hide)

Self Reflection Have you mastered the following important concepts? • Types of metabolism • General characteristics of enzymes

• Mechanism of enzyme action • Factors that influence the mechanism of enzyme action • Application of enzymes in daily life

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Summative Practice 5 1 Some chefs sometimes wrap meat in papaya leaves and the meat is marinated for 5 hours before it is cooked. What is the purpose of wrapping with papaya leaves? 2 Why are apples that have been boiled after they are peeled, do not change colour to brown? 3 (a) Enzymes are used in industries and everyday life. Explain the use of enzymes to extract agar-agar from seaweed. (b) State one function of lipase in the food industry. 4 (a) State two characteristics of enzymes. (b) Explain why only certain substrate can combine with enzymes. (c) (i) What is the hypothesis that is used to explain the mechanism of enzyme action? In this hypothesis, what represents the structure of enzymes and the structure of the substrate? (ii) Which characteristics of enzymes can explain this hypothesis? Essay Questions 5 (a) If you are a food entrepreneur, suggest an enzyme that you can use to process meat and fish. State the function of this enzyme. (b) Discuss how the characteristics of the enzymes can influence its action. Enrichment 6 The enzymes that exist in the bacteria strain which live in hot spring areas can be extracted and added to laundry detergent. Suggest why enzymes from these bacteria are suitable to be used as laundry detergent. 7 Why does cyanide poisoning cause immediate death?

8 Fresh fruits can be processed to produce juice. Fruits are crushed and squeezed before the juice is extracted. Plant cells contain strong cellulose walls. However, if enzymes that contain pectinase enzymes are used, more juice can be extracted. Based on this information, suggest one laboratory experiment that can extract more fruit juice than the pressing method.

Complete answers are available by scanning the QR code provided

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6

CHAPTER

Cell Division

Do You KNOW…

Can identical organisms be produced?

• How does grow th happen? • How does an or ganism produce new cells? • How is genetic variation created?

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6.1 Cell Division 6.1.1 Describe: • karyokinesis (nuclear division) • cytokinesis (cytoplasmic division) 6.1.2 Describe the terms haploid, diploid, chromatin, homologous chromosomes, paternal chromosome and maternal chromosome. 6.2 Cell Cycle and Mitosis 6.2.1 Describe the phases in a cell cycle: • interphase • G1 phase • S phase • G2 phase • M phase • mitosis • cytokinesis 6.2.2 Arrange the stages of mitosis in the correct order. 6.2.3 Communicate about the cell structure of each stage of mitosis and cytokinesis by using labelled diagrams. 6.2.4 Compare and contrast mitosis and cytokinesis in animal and plant cells 6.2.5 Discuss the necessity of mitosis in: • development of embryo • growth of organisms • healing of wounds on the skin • regeneration • asexual reproduction

6.3 Meiosis 6.3.1 State the meaning of meiosis. 6.3.2 Identify types of cells that undergo meiosis. 6.3.3 State the necessity of meiosis in: • the formation of gametes (gametogenesis). • producing genetic variation • maintaining diploid chromosomal numbers from one generation to another. 6.3.4 Explain the stages of meiosis in the correct order: • meiosis I • meiosis Il 6.3.5 Draw and label the cell structure in each stage of meiosis I, meiosis II and cytokinesis. 6.3.6 Compare and contrast meiosis and mitosis. 6.4 Issues of Cell Division on Human Health 6.4.1 Explain the effects of abnormal mitosis on human health: • tumour • cancer 6.4.2 Evaluate the effects of abnormal meiosis on Down syndrome individuals.

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6.1 Brainstorm! What happens when cells cannot undergo cell division?

Cell Division Cells in our body always grow, divide and die. As such, the dead cells must be replaced with new cells. Cells in the body produce new cells through the cell division process. Cell division involves two stages, that is karyokinesis and cytokinesis. • Karyokinesis involves the division of the nucleus. • Cytokinesis involves the division of the cytoplasm. The organism’s body cells are divided into somatic cells and reproductive cells or gametes. ORGANISM CELL SOMATIC CELL • •

Body cells apart from gametes. Somatic cells are produced through the mitosis process. It contains a diploid number of chromosomes, that is, each cell contains two sets of chromosomes or 2n. In human somatic cells, 2n = 46.



GAMETE • • •

Gametes are reproductive cells. Gametes are produced through the meiosis process. It contains a haploid number of chromosomes, that is, each cell contains one set of chromosomes or n. In human gametes, n = 23.

In diploid cells, one set of chromosomes originate from the male parent or paternal chromosomes and another set is from the female parent or maternal chromosomes. Both paternal and maternal chromosomes have the same structural characteristics. This pair of chromosomes are called homologous chromosomes (Figure 6.1). Chromatin is a chromosome that looks like a long thread. Haploid (n) A copy (n) Aofcopy eachofset each of set chromosome of chromosome Haploid (n): AHaploid copy of each chromosome

(2n) Two copies Two copies of eachofchromosome each chromosome Diploid Diploid (2n):Diploid Two(2n)copies of each chromosome

ICT 6.1 Importance of cell division (Accessed on 21 August 2019)

Three pairs of homologous chromosomes (one setThree of paternal chromosomes, one set of Three pairs ofpairs homologous of homologous chromosome chromosome set (one of set paternal of paternal chromosomes, chromosomes, one setone of set of maternal(one chromosomes) maternal maternal chromosomes) chromosomes) FIGURE 6.1 Haploid and diploid chromosomes

Three chromosomes without pairs

Three Three chromosomes chromosomes withoutwithout pairs pairs

Formative Practice

6.1

1 Give the definition of the following terms:

(a) karyokinesis (c) chromatin

(b) cytokinesis

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(d) homologous chromosomes

2 Predict what will happen if the cells in the reproductive organs of humans are unable to produce haploid cells. 6.1.1

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6.2

Cell Cycle and Mitosis What is a cell cycle? The cell cycle refers to the sequence of events that involves DNA multiplication and cell division to produce two daughter cells. The cell cycle consists of interphase and M phase. Interphase is the longest phase in the cell cycle. This phase is made up of the G1, S and G2 phase. S PHASE The DNA in the nucleus is replicated. Each chromosome multiplies into two identical chromosomes known as sister chromatids. Both chromatids contain the same copy of the DNA molecule. Both chromatids are joined at the centromeres.

1 Cells grow. Cell components such as mitochondrion and endoplasmic reticulum are produced at this stage. Proteins used in the cell cycle are also synthesised during this time. At this stage, the nucleus looks big and the chromosome is in the form of chromatin.

INTER

PH

CHAPTER 6

2 DNA synthesis occurs in the S phase.

G1 PHASE

AS E

S G1

MP

Mitosis

Cyt

oki

nes

is

G2

HAS

E

FIGURE 6.2 Cell cycle

M PHASE 4 M phase is made up of mitosis

and cytokinesis. Mitosis involves prophase, metaphase, anaphase and telophase.

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G2 PHASE 3 The cells will continue to grow and remain active

metabolically during the G2 phase. Cells gather energy and make final arrangements to enter the next stage of cell division. After the interphase stage, the cell will enter the M phase.

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Our World of Biology The failure of mitotic division in somatic cells will not be inherited by the next generation.

Mitosis Mitosis is defined as the division of the nucleus of parent cell into two nuclei (Photograph 6.1). Each nucleus contains the same number of chromosomes and genetic content with the nucleus of parent cell. centriole spindle fibres

PROPHASE

• • • •

In the nucleus, chromatin starts to shorten and thicken to form a chromosome structure that can be seen through a light microscope. The chromosome is seen to be made up of two identical threads called sister chromatids. Both sister chromatids are joined at the centromere. The nucleus membrane disintegrates, the nucleolus disappears, the centriole moves to the opposite poles and spindle fibres start to form.

centromere nucleus membrane disintegrates chromosomes

the

centromere

ICT 6.2

anaphase telophase

Activity: Design three dimensional models of the mitotic stages

prophase

metaphase

PHOTOGRAPH 6.1 Mitosis at the tip of the plant root

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6.2.2

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equatorial plane centromere

spindle fibres

METAPHASE

• •



Centrioles are at the opposite poles of the cell. The spindle fibres maintain the chromosomes at the equatorial plane. The chromosomes become aligned in a single row on the equatorial plane. Metaphase ends when the centromere begins to divide.

chromosomes

chromosomes

sister chromatids ANAPHASE



TELOPHASE

• • • • • • •

When the chromatids are at the opposite poles, they are now called the daughter chromosome. Each pole contains one set of complete and identical chromosomes. Chromosomes are shaped again as fine chromatin threads. Nucleoli are formed again. Spindle fibres disappear. A new nucleus membrane is formed. The telophase stage is followed by cytokinesis.





The centromere divides into two and the sister chromatids separate. Spindle fibres shorten, contract and the sister chromatids are attracted to the opposite pole cells. Anaphase ends when the chromatid arrives at the pole of the cell.

daughter chromosomes

CHAPTER 6



pole of the cells

spindle fibres centriole

nuclear membrane sister chromatids nuclear membrane daughter cells FIGURE 6.3 Mitosis 6.2.2

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cleavage furrow

microfilaments

The differences between mitosis and cytokinesis in animal cells and plant cells Plant cells do not contain centrioles. However, plant cells can still form spindle fibres during mitosis. Cytokinesis is different between animal cells and plant cells. Cytokinesis is the division of cytoplasm that happens immediately after the nucleus is formed, that is, at the end of telophase. Cytokinesis occurs in animal cells when the plasma membrane constricts in the middle of the cell between the two nuclei (Figure 6.4). Microfilaments at the point of constriction will contract, causing the cell to constrict until it splits to form two daughter cells. Cytokinesis in plant cells also begins when the formed vesicles combine to form cell plates at the centre of the cell (Figure 6.5). The cell plates are surrounded by a new plasma membrane and a new cell wall substance is formed among the spaces of the cell plates. The cell plates expand outwards until they combine with the plasma membranes. At the end of cytokinesis, cellulose fibres are produced by the cells to strengthen the new cell walls. Two daughter cells are formed. Each cell has a diploid condition.

contractile ring of microfilaments

daughter cell FIGURE 6.4 Cytokinesis in animal cells

vesicles form cell plates

parent cell wall cell plate

new cell wall

FIGURE 6.5 Cytokinesis in plant cells

daughter cell

The necessity of mitosis For embryo development and organism growth, mitosis ensures that rapid cell growth occurs.

Mitosis is important for the following life processes. Through the mitosis process, the lizard is able to grow a new tail (regeneration) if the tail breaks.

When the body is injured, mitosis will produce new cells to replace cells that are dead or damaged.

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Mitosis aids organisms such as hydra to produce new individuals through the formation of new buds. PHOTOGRAPH 6.2 The necessity of mitosis for living organisms 6.2.4

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Stem cell therapy uses stem cells from bone marrows to treat damaged cartilage.

In agriculture, the technique of culturing plant tissues is used to produce young plants through the culturing of parent cells without going through the fertilisation process.

The culturing technique uses stem cells from animals which are then cultured in laboratories to produce meat.

6.2

1 State the application of mitosis in the field of agriculture.

3 Predict what will happen if the spindle fibres fail to develop.

2 Explain the process that occurs during the S phase.

4 Explain the necessity of mitosis for life processes.

6.3

PHOTOGRAPH 6.3 The application of mitosis in the fields of medicine and agriculture

CHAPTER 6

Formative Practice

Meiosis Meiosis is the process of cell division that occurs in reproductive organs to produce gametes that contain half the number of chromosomes (haploid) of the parent cells (diploid). Meiosis occurs in the testis (male) and ovary (female) for animals and humans.

The need for meiosis Meiosis forms gametes through the process of gametogenesis and ensures that the diploid chromosome number of organisms that carry out sex reproduction is always maintained from one generation to the next. Meiosis also produces genetic variation in the same species. Meiosis is divided into two stages of cell division, that is meiosis I and meiosis II (Figure 6.6). a. Meiosis I comprises of prophase I, metaphase I, anaphase I and telophase I. b. Meiosis II comprises of prophase II, metaphase II, anaphase II and telophase II. PHOTOGRAPH 6.4 Homologous chromosome

6.3.1

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6.3.3

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non-identical chromatid

chiasma

PROPHASE I •

Chromatin shortens, thickens and forms visible chromosomes. The pairing of homologous chromosomes (synapsis) forms bivalent (or known as a tetrad, that is four chromatids for each homologous chromosome).



The crossing over process that is an exchange of genetic material between non-identical chromatids takes place. Crossing over produces a combination of genes that are new in chromosomes. The point where the chromatids cross over is called chiasma. At the end of prophase I, the nucleus membrane and nucleoli will start to disappear. Both centrioles will move towards the opposite pole cells. Spindle fibres are formed among the centrioles.

spindle fibre

bivalent/ tetrad centriole

homologous chromosome separated and pulled to opposite poles

sister chromatids are still tied to the centromere

plasma membrane constricts equatorial plane FIGURE 6.6 Meiosis

homologous chromosome arranged at the equatorial plane

METAPHASE I •

The homologous chromosomes are arranged at the equatorial plane.



One chromosome from each pair of the homologous chromosome is tied to the spindle fibres from one pole cell and its homologous is tied to the spindle fibres from the opposite pole cell.



The sister chromatids are still tied together because the centromere has not separated.

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centriole

TELOPHASE I

ANAPHASE I •



The spindle fibres contract and cause each homologous chromosome to separate from its homologous pair and be pulled to the opposite poles.



The chromosomes arrive at the opposite pole cells.



Each polar cell contains a number of haploid chromosomes that are made up of one set of chromosomes only.

Each chromosome is still made up of a pair of sister chromatids tied to a centromere and move as one unit.



The spindle fibres will then disappear.



Nucleoli will reappear and the nuclear membrane is formed.



Telophase I is succeeded by the cytokinesis process that produces two daughter cells.



Both daughter cells produced are in the haploid condition.



The interphase for meiosis I is usually short and the DNA does not replicate. 6.3.4

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PROPHASE II

ANAPHASE II



The nucleoli and the nuclear membrane disappear.





Each chromosome is made up of sister chromatids that are joined at the centromere.





The spindle fibres start to form in both daughter cells.

The sister chromatid centromere starts to separate. The sister chromatid pair separates and moves towards the opposite poles led by the centromere. Each chromatid at this stage is known as a chromosome.



four haploid daughter cells

CHAPTER 6

sister chromatids separate

nuclear membrane

two haploid daughter cells

METAPHASE II

TELOPHASE II



Chromosomes are arranged at random on the equatorial plane for each daughter cell.

• •



Each chromatid is tied to the spindle fibres at the centromere.





Metaphase II ends when the centromere separates.

6.3.4

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• •

Chromosomes arrive at the pole of the cell. Spindle fibres disappear. The nuclear membrane and the nucleoli are reconstructed. The number of chromosome for each daughter cell is half the number of parent chromosomes. Telophase II ends with the process of cytokinesis that produces four daughter cells that are haploid. Each haploid cell contains half the number of parent cell chromosomes. The genetic content is also different from the diploid parent cell. The haploid cells develop into gametes.

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Comparison and contrast between meiosis and mitosis

Activity Zone

You have learned about two types of cell divisions, that is the mitosis and meiosis. What is the main event that differentiates mitosis and meiosis and between meiosis I and meiosis II? Compare and contrast the two types of cell division.

Build a thinking tool to compare and contrast: (a) meiosis I and meiosis II (b) meiosis and mitosis

Formative Practice

6.3

1 State the most obvious difference between meiosis I and meiosis II.

6.4 ICT 6.3 Video: Cancer (Accessed on 21 August 2019)

2 Explain how meiosis I can reduce the number of chromosomes in the daughter cell.

Issues of Cell Division on Human Health The cell cycle is controlled by a special control system at each G1, S, G2 and M phase to ensure proper division of the cells. However, uncontrolled cell division sometimes can lead to the formation of tumours. Tumour is divided into two types which are benign tumour and malignant tumour. A benign tumour is not dangerous and can be removed surgically. A malignant tumour is also called cancer. Cancer is caused by several factors such as radiation (x-ray, gamma rays and ultraviolet rays), chemical substances (such as tar in tobacco), carcinogens (such as formaldehyde and benzene), genetic factors, and also bacteria and viruses. This will cause the cells to divide continuously and develop into a tumour. The cancer cells will spread and destroy normal cells around them. This condition will affect the functions of the tissues around them. Cancer that is not identified at the early stage can cause damage to the organs and finally death (Figure 6.7).

lymph vessel

a tumour

grandular tissues

The tumour grows from a single cell.

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blood vessel

Cancer cells compete to get nutrients from other tissues around them.

cancer cell

The cancer cells spread A new tumour through the lymph vessels and develops on other blood vessels to other parts of organs. the body.

FIGURE 6.7 The development of breast cancer

6.3.6

6.4.1

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Any abnormality during the division of meiosis can also cause genetic diseases such as Down syndrome. This happens because the spindle fibres fail to function during anaphase I or anaphase II. As a result, the chromosome fails to separate (nondisjunction). Gametes will have an abnormal number of chromosomes (22 or 24 chromosomes). If fertilisation between a normal gamete (23 chromosomes) and an abnormal chromosome (24 chromosomes) occurs, the zygote will carry 47 chromosomes which is an abnormal condition (Figure 6.8). In a normal meiosis division, the chromosomes are divided evenly among the gametes.

If the homologous chromosome or sister chromatids fail to separate, the distribution of parent chromosomes during meiosis will be uneven.

The diploid chromosome number in humans 2n = 46

PHOTOGRAPH 6.5 A child with Down syndrome displays certain characteristics such as stunted body growth and mental retardation

MEIOSIS

CHAPTER 6

The diploid chromosome number in humans 2n = 46

MEIOSIS nondisjunction during anaphase

The haploid number

The haploid number

The haploid number

The haploid number

n = 23

n = 23

n = 24

n = 22

PHOTOGRAPH 6.6 The complete chromosome set of an individual with Down syndrome

FERTILISATION

Diploid chromosome number, 2n +1= 47 ( Three copies of chromosome 21 ) FIGURE 6.8 Formation of trisomy 21

An individual with Down syndrome has 47 chromosomes, which is an extra chromosome at the 21st set. This condition is known as trisomy 21. This syndrome can cause mental retardation, slanted eyes and a slightly protruding tongue. Formative Practice

6.4

1 Explain why radiotherapy is used to control or stop the growth of cancer cells.

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2 Nondisjunction conditions in humans can cause genetic diseases such as Down syndrome. State the number of chromosomes and the characteristics that are found in an individual with Down syndrome.

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Summary CELL DIVISION

Cell Division

Cell Cycle and Mitosis

Karyokinesis (nuclear division)

M phase (mitosis and cytokinesis)

Cytokinesis (cytoplasmic division)

Interphase (G1, S and G2 phase)

Meiosis

Meiosis I and meiosis II The similarities and differences between meiosis and mitosis

Issues of Cell Division on Human Health

The effects of mitosis abnormality: tumour, cancer The effects of meiosis abnormality: Down syndrome

Self Reflection Have you mastered the following important concepts? • Definitions of karyokinesis, cytokinesis, haploid, diploid, chromatin, homologous chromosomes, paternal and maternal chromosomes • Cell cycle • Stages of mitosis • The differences bet ween mitosis and cytokinesis bet ween animal cells and plant cells • Stages of meiosis • Differences and similarities bet ween meiosis and mitosis • The need for mitosis and meiosis • The effects of mitosis and meiosis abnormalit y towards human health

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Summative Practice 6 1 Name the sequences in the mitosis process. 2 What is the function of the centriole in the division of animal cells? 3 State one difference between mitosis metaphase and meiosis metaphase I. 4 (a) Explain the importance of cell division that happens at the tip of a plant root. (b) A farmer wants to plant a large number of quality breed mango trees in a short time for commercial purposes. State and explain the techniques that can be used by the farmer.

5 Figure 1 shows a cell at stage M in a cell cycle. Draw both cells that will be formed if the P chromosome does not separate. Essay Questions 6 Figure 2 shows the complete set of chromosomes of an individual. (a) State the genetic disorder this individual has. (b) Explain how this individual is born with this genetic disorder.

chromosome PPchromosome

FIGURE 1 Answer

FIGURE 2

7 Cancer cells are formed after normal cells are exposed to factor Y. (a) Explain the formation of cancer cells. (b) State two examples of factor Y that causes the formation of cancer cells. (c) State two ways to avoid the development of cancer cells. Enrichment 8 The development of plant tissue culture has allowed scientists to improve the quality and quantity of a crop. Scientists in Malaysia have succeeded in patenting a product that can be sprayed on orchid plants to overcome infections caused by a virus. This branch of biotechnology is called RNA interference technology. In your opinion, can the spray technology be used for all organisms as protection against infections? Complete answers are available by scanning the QR code provided

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7

CHAPTER

Cellular Respiration

Do you KNOW...

How is tempe processed?

• Why is energy re quired for the metabolic process? • What is the main substrate in the production of ener gy? • What are the typ es of respiration? • What are the proc esses that occur in aerobic re spiration and fermentation?

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7.1 Production of energy through cellular respiration 7.1.1 Justify the necessity of energy in metabolic processes. 7.1.2 Identify the main substrate used in energy production. 7.1.3 List the types of cellular respiration: • aerobic respiration • anaerobic respiration • fermentation 7.2 Aerobic respiration 7.2.1 Conceptualise energy production from glucose during aerobic respiration in cells. 7.2.2 Write a word equation for aerobic respiration in cells. 7.2.3 Conduct an experiment to study aerobic respiration. 7.3 Fermentation 7.3.1 State the factors that cause fermentation to occur in cells. 7.3.2 Explain by using examples of energy production from glucose during fermentation in: • human muscle cells • Lactobacillus • yeast • plants such as paddy 7.3.3 Write and explain word equations for: • lactic acid fermentation • alcohol fermentation 7.3.4 Conduct an experiment to study fermentation in yeast. 7.3.5 Compare and contrast aerobic respiration and fermentation.

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7.1

Production of energy through cellular respiration In Chapter 5, you have learned about two types of metabolic reaction, which are anabolism and catabolism. Both of these reactions involve energy. • The catabolism process releases energy. • The anabolism process uses energy. Without energy, the anabolic processes such as protein formation which is the basic muscle substance will not occur.

Activity Zone Conduct a group discussion about the energy requirements in the metabolic process.

The main substrate in energy production Cellular respiration is carried out to generate the energy needed by all living cells. Cellular respiration is the oxidation process of organic molecules through several stages to release energy. The main substrate for cellular respiration is glucose. Chemical energy found in glucose is released to produce energy required by cells. In humans and animals, glucose is obtained through the digestion of carbohydrates from the food eaten. In green plants, light energy can be trapped by chlorophyll for the photosynthesis process to produce glucose.

Types of cellular respiration

There are two types of cellular respiration, which are aerobic and anaerobic respiration. Aerobic respiration occurs in the presence of oxygen. Anaerobic respiration occurs in the absence of oxygen. Fermentation is an alternative pathway of obtaining energy besides cellular respiration. In fermentation, the breakdown of glucose is incomplete in conditions of limited oxygen or without oxygen. This chapter focuses only on aerobic respiration and fermentation.

Formative Practice

7.1

1 Give five examples of the necessity of energy in a metabolic process.

4 Explain how humans, animals and plants acquire glucose to produce energy.

2 State the main substrate in the production of energy. 3 State the meaning of cellular respiration and the types of cellular respiration.

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7.1.1

7.1.2

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ICT 7.1 Video: Aerobic respiration (Accessed on 21 August 2019)

Aerobic respiration is the breakdown of glucose involving oxygen to produce chemical energy. Oxygen is used to oxidise glucose to produce carbon dioxide, water and energy. The aerobic respiration process begins with the glycolysis process. Glycolysis means the breakdown of glucose by enzymes. This process occurs in the cytoplasm. One glucose molecule is broken down into two pyruvate molecules. The following process occurs in the mitochondrion. Pyruvate produced from glycolysis is then oxidised through a series of reactions to produce carbon dioxide, water and energy. A large amount of this energy is used to produce adenosine triphosphate (ATP) molecules. Glycolysis

Brainstorm! The number of mitochondrion in the muscle cells of an athlete increases after intensive training. Explain how this contributes to the achievement of the athlete as compared with those who do not undergo intensive training.

Oxidation of Pyruvate Carbon dioxide + water + energy

Glucose Pyruvate (Occurs in the cytoplasm)

(Occurs in the mitochondrion)

The aerobic respiration is simplified as follows. • ATP molecules are produced when a group of non-organic phosphate is added to adenosine diphosphate (ADP). ADP + phosphate • •

energy

CHAPTER 7

7.2

Aerobic Respiration

ATP

ATP molecules have weak phosphate links. When the phosphate links on ATP molecules are broken, the energy released is supplied to cells to help us carry out our daily activities.

ATP

energy

ADP + phosphate

The complete process of glucose oxidation is simplified as follows: Word equation: Glucose + oxygen

7.2.1

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Carbon dioxide + water + energy (2898 kJ)

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seActivity i1 ti.v2itcA

7.1

To study aerobic respiration

Experiment

Problem statement Do living organisms carry out aerobic respiration?

Hypothesis Living organisms use oxygen and release carbon dioxide during aerobic respiration.

Variable Manipulated: Presence of living organisms Responding: Increase in the level of coloured liquid Fixed: Initial level of coloured liquid

Take Note! Wipe all connectors with petroleum jelly to ensure that the apparatus prepared is airtight.

Materials Water, coloured liquid, soda lime, living organism (cockroach) and petroleum jelly

Apparatus Boiling tubes, screw clip, wire gauze, 250 ml beaker, capillary tube, ruler, rubber tube and water bath



screw clip

Biological Lens

rubber tube capillary tube

capillary tube

boiling tube A cockroach wire gauze

boiling tube B

level of coloured liquid

level of coloured liquid soda lime



The apparatus set-up is called a respirometer. It is used to measure the rate of respiration of an organism by estimating the rate of oxygen used.

water bath to maintain temperature

Apparatus set-up to study aerobic respiration process

Procedure 1 Prepare the apparatus as shown in the figure above. 2 Prepare two boiling tubes labelled A and B. 3 Fill both boiling tubes with 10 g soda lime. 4 Put the wire gauze in the middle of boiling tube A. 5 Put a cockroach on the wire gauze in boiling tube A while the boiling tube B is left empty. 6 Wipe all connections of the apparatus with petroleum jelly. 7 Close the screw clip and mark the height of the initial level of the coloured liquid in the capillary tube for both boiling tubes. 8 Leave the apparatus for an hour. 9 Measure and record the final height of the coloured liquid in both capillary tubes after an hour with a ruler. 10 Record your observations in the following table.

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Results Boiling tube

Initial level (cm)

Final level (cm)

Difference in levels (cm)

A B

Discussion 1 What is the purpose of preparing boiling tube B? 2 What is the function of soda lime in the boiling tube? 3 Is there a change in the level of coloured liquid in capillary tube A? Explain your answer.

Conclusion

Formative Practice

7.2

1 State the meaning of aerobic respiration. 2 Suggest another substrate apart from glucose that can be used by cells for cellular respiration.

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CHAPTER 7

Is the hypothesis accepted? Suggest a suitable conclusion.

3 State the word equation for aerobic respiration. 4 Describe the processes involved in aerobic respiration to produce energy.

Fermentation Fermentation is the incomplete breakdown of glucose in conditions of limited oxygen or without oxygen. Fermentation is different from aerobic respiration in its metabolic pathway after the glycolysis stage. After glycolysis, the pyruvate produced will undergo either alcohol fermentation or lactic acid fermentation.

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FERMENTATION The incomplete breakdown of glucose in limited or no oxygen conditions. ICT 7.2 Video: Anaerobic respiration (Accessed on 21 August 2019)

ALCOHOL FERMENTATION The incomplete breakdown of glucose to ethanol, carbon dioxide and energy.



Glucose

Ethanol + carbon dioxide + energy (210 kJ)

YEAST

PLANTS



Ethanol is used in the making of beer and wine.



Paddy plants that grow in waterlogged areas with less oxygen are able to carry out alcohol fermentation.



The released carbon dioxide makes bread dough rise.



Ethanol produced in the tissues during the fermentation process is toxic to most plants but the cells of paddy plants have a higher tolerance for ethanol compared to other species.



Paddy plants produce plenty of alcohol dehydrogenase enzymes that can break down ethanol molecules into non-toxic carbon dioxide.

.

seActivity it1 iv.i2tcA 7.2

Produce and market food products produced through fermentation

Project

Procedure 1 Your teacher will divide your class into a few groups. 2 Each group will choose one food product that is produced through the fermentation process and market that product in school. Examples of products are tapai, yoghurt or bread. 3 Each group needs to prepare a proposal before starting the project. The proposal must contain:



• • • •

introduction of the project including the objectives execution cost production and marketing plan expected outcome

4 If necessary, get advice from your teacher or parents to ensure the smooth delivery of the project. 5 Conduct the project as planned. 6 At the end of the project, each group must prepare a complete report.

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Lactobacillus bacteria

LACTIC ACID FERMENTATION The breakdown of glucose into lactic acid and energy.



Glucose

Lactic acid + energy

Brainstorm!

LACTOBACILLUS The bacteria Lactobacillus carries out milk fermentation to produce yoghurt.



Lactobacillus acts on the lactose (milk sugar) and turns it into lactic acid.



The lactic acid will then coagulate casein (milk protein) to produce yoghurt.



Lactic acid is the source of a sour taste in yoghurt.

Some bacteria can only survive in anaerobic conditions. Predict what can happen to this type of bacteria when oxygen is supplied. CHAPTER 7



HUMAN MUSCLE CELLS •

This process is carried out by the muscle cells during vigorous training.



During vigorous training, the rate of oxygen used exceeds the oxygen supplied by the blood circulatory system.



The muscle is in an oxygen-deficiency state and is said to undergo oxygen debt.



During this process, glucose cannot break down completely. For each glucose molecule that is broken down, only two ATP molecules or 150 kJ energy will be produced.



The produced lactic acid accumulates until it reaches a level of concentration that can cause fatigue and muscle cramps.



Once the vigorous activity stops, the intake of excess oxygen will oxidise the lactic acid into carbon dioxide, water and energy. When all the lactic acid has been expelled, the oxygen debt is repaid.

recovery

lack of oxygen (oxygen debt) oxygen intake

• Figure 7.1 shows a lack of oxygen in muscles and oxygen debt is repaid.

exercise

oxygen intake during exercise

at the beginning of exercise

oxygen debt repaid

at the end of exercise

at the end of recovery

Time (minutes) FIGURE 7.1 Lack of oxygen in muscles and oxygen debt repaid 7.3.2

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se1it.2 ivitc7.3 A Activity

To study the process of yeast fermentation

Experiment

Problem statement What are the products of yeast fermentation?

Hypothesis Yeast fermentation produces energy, carbon dioxide and ethanol.

Variables

Take Note!

Manipulated: Presence of yeast Responding: Changes in temperature, lime water and ethanol smell Fixed: The volume of boiled glucose solution and the anaerobic condition

Ensure that the end of the delivery tube is soaked in lime water.

Materials 5% yeast suspension, 5% boiled glucose solution, lime water and paraffin oil

thermometer

90

100

110

thermometer

70 20 10 0

2 Label the boiling tubes as A and B.

110 100 90 80 70 60 50 40 20

20 10 0 -10 10

lime

yeast below. 8 Record your observationssolution in the+table water suspension

5% boiled glucose solution

30

70 60 50 40

boiling tube B

30

7 Measure and record the initial and final temperature paraffin using a oil thermometer. 5% boiled glucose

thermometer

5% boiled glucose solution

10

80

boiling

6 Leave the apparatus for 1 hour. tube A

paraffin oil lime water

delivery tube

0

90

100

110

5 Close both boiling tubes with the cork that has a hole and delivery a delivery tube. Prepare 2 test tubetubes with 2 ml of lime water respectively. Dip the end of each delivery tube into each test thermometer tube that contains lime water.

-10 10 0

4 Add paraffin oil into both of the boiling tubes.

-10 10

5% boiled glucose solution + yeast suspension

3 Put 5 ml 5% yeast suspension into boiling tube A.

paraffin oil lime water

Apparatus set-up to study the yeast fermentation process

Results Boiling tube

boiling tube B

80

boiling tube A

30

been boiled and left to cool.

delivery tube

60

Procedure 1 Fill 2 boiling tubes with 15 ml of 5% glucose solution that has

delivery tube

50

Boiling tube, test tube, thermometer, measuring cylinder, delivery tube and cork

40

Apparatus

Temperature (°C) Beginning of experiment

End of experiment

Change in lime water

Smell of solution

A B

Discussion 1 How is the anaerobic condition maintained to ensure that the fermentation process is complete? 2 What is the function of preparing boiling tube B?

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3 What is the purpose of boiling the glucose solution earlier? 4 How do the results show that fermentation has taken place in boiling tube A?

Conclusion Is the hypothesis accepted? Suggest a suitable conclusion.

Comparison between aerobic respiration and fermentation There are a few similarities and differences between fermentation and aerobic respiration (Figure 7.2 and Table 7.1). The process begins in the cytoplasm

Occurs in yeast, bacteria, animals and plants

SIMILARITIES BETWEEN AEROBIC RESPIRATION AND FERMENTATION Produces chemical energy in the form of ATP

Brainstorm! Why is aerobic respiration more suitable for yeast compared with fermentation?

CHAPTER 7

The breakdown process of glucose and its conversion to chemical energy

The process begins with glycolysis when glucose is converted to pyruvate

FIGURE 7.2 Similarities between aerobic respiration and fermentation TABLE 7.1 Differences between aerobic respiration and fermentation DIFFERENCES Aerobic Respiration

Fermentation

The breakdown process of glucose is completed in the presence of oxygen.

The breakdown process of glucose is incomplete without oxygen or in limited oxygen conditions.

Occurs in cytoplasm and mitochondrion.

Occurs in cytoplasm.

Produces water.

Does not produce water.

Glucose is oxidised completely into carbon dioxide and water.

Glucose is not oxidised completely into ethanol and carbon dioxide or lactic acid.

One molecule of glucose generates 2898 kJ of energy

One molecule of glucose generates 210 kJ (alcoholic fermentation) or 150 kJ (lactic acid fermentation) of energy

Formative Practice

7.3

1 State where the process of fermentation usually occurs. 2 Give three examples of microorganisms and food produced by the fermentation process.

cellular respiration that takes place in the muscle cells of your legs. 4 State the differences between aerobic respiration and fermentation.

3 While helping your father to cut the grass at the farm, you come across a snake. Terrified, you run away from the snake. Explain the 7.3.5

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Summary CELLULAR RESPIRATION

Production of energy through cellular respiration

The main substrate in energy production is glucose

Occurs in cytoplasm Glucose Pyruvate

Aerobic Respiration

Anaerobic Respiration

The breakdown of glucose in the presence of oxygen to produce chemical energy

Fermentation

The incomplete breakdown of glucose in limited oxygen or no oxygen

Occurs in mitochondrion (pyruvate oxidation) Carbon dioxide + water + energy • Alcohol fermentation • Lactic acid fermentation

Self Reflection Have you mastered the following important concepts? • The necessit y of energy in metabolic processes

• The main substrate in the production of energy • Types of cellular respiration

• Energy production from glucose during aerobic respiration in cells • Word equation for aerobic respiration in cells

• Factors that cause fermentation to occur in cells

• Example of energy production from glucose during fermentation • Lactic acid fermentation and alcohol fermentation • Yeast fermentation process

• Differences bet ween aerobic respiration and fermentation

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Summative Practice 7 1 What are the uses of alcohol fermentation products? 2 Why do muscles carry out cellular respiration that produces lactic acid during vigorous training? 3 Why does cellular respiration in muscles that produce lactic acid supply less energy compared to aerobic respiration? 4 Explain why an individual usually feels tired faster compared with an athlete, when both of them are running together. 5 A 100-metre sprinter usually holds his breath while running compared with a long-distance runner. After running, the sprinter needs seven litres of oxygen to remove the lactic acid in his muscle cells. Explain this difference between the sprinter and the long-distance runner.

CHAPTER 7

6 Photograph 1 shows the activities by two individuals, P and Q.

P Q PHOTOGRAPH 1

(a) (i) Based on Photograph 1, identify the respiration that occurs in the muscles of individuals P and Q. (ii) State the products of respiration in P and Q. (b) During the 100-metre sprint on Sports Day, a pupil experienced muscle cramps and had to stop running. Explain why muscle cramps happen. (c) Paddy plants grown in waterlogged areas have tolerance to ethanol compared with other plants. (i) State the type of fermentation that occurs in paddy plant cells. (ii) Write the word equation for the fermentation process that occurs in the paddy plant cells. (iii) Suggest another cell that can carry out the fermentation process as in question c(ii).

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Essay Questions 7 (a) Explain why energy is required in metabolic processes. (b) Compare aerobic respiration with fermentation. (c) Microorganisms such as yeast and bacteria usually play an important role in the fermentation process to produce food. Explain why yoghurt can spoil if it is not kept in the refrigerator. Enrichment 8 A person who is not used to exercising will experience muscle cramps when doing vigorous exercise because of the accumulation of lactic acid in the cells. However, for high-performance athletes, such problems do not occur because their bodies have a high tolerance for lactic acid. In your opinion, how do high performance athletes overcome the problem of lactic acid accumulation? Give your reasoning. 9 Studies have shown that intake of sodium bicarbonate or baking powder (baking soda) can increase muscle efficiency during intense activities that involve muscle fermentation. Give your justification. 10 While conducting an experiment using yeast, Mei Ling found that if grape juice is kept with yeast in a covered container, the yeast will slowly break down the glucose in the grapes. However if the container does not contain any oxygen, the yeast will break down the glucose at a faster rate, and the alcohol content in the container will rise very fast. At the end of the experiment, Mei Ling found that the breakdown rate of glucose becomes slow again even though there are some grapes that have not been oxidised. Explain Mei Ling’s observation. 11 Susan tried to make bread using dry yeast bought from a shop. When she mixed the yeast with plain flour, she found that her bread did not rise after half an hour. Explain how you can help Susan solve her problem.

Complete answers are available by scanning the QR code provided

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2

THEME

PHYSIOLOGY OF HUMANS AND ANIMALS This theme aims to provide an understanding of the physiological processes in humans and animals. This theme focuses on physiological processes, which are respiration, nutrition, sensitivity, excretion, movement, reproduction and growth as well as cell division.

Chapter 8 Respiratory System in Humans and Animals Chapter 9 Nutrition and the Human Digestive System Chapter 10 Transport in Humans and Animals Chapter 11 Immunity in Humans Chapter 12 Coordination and Response in Humans Chapter 13 Homeostasis and the Human Urinary System Chapter 14 Support and Movements in Humans and Animals Chapter 15 Sexual Reproduction, Development and Growth in Humans and Animals

8

CHAPTER

Respiratory Systems in Humans and Animals

Do You KNOW…

Why is the respiratory system important to humans and animals?

• What are the dif ferent respiratory str uctures found in: • insects • amphibians • fish • humans • What are the ad ap structures and theirtations of respiratory functions in gaseou exchange? s • What are the brea th in humans and animing mechanisms found als? • How does gaseou s exchange betwee lungs and blood, an n d between blood an tissues occur? d • How does the tra ns from lungs to tissu port of respiratory gases es and from tissues lungs occur? to • What are the he alth human respiratory issues related to the system?

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8.1 Types of Respiratory System 8.1.1 Identify respiratory structures in: • insects • fish • amphibians • humans 8.1.2 Describe the adaptation of respiratory structures and their functions for gaseous exchange in: • animals • humans 8.1.3 Compare and contrast respiratory structures in humans and animals. 8.2 Mechanisms of Breathing 8.2.1 Compare and contrast breathing mechanisms in humans and animals. 8.3 Gaseous Exchange in Humans 8.3.1 Communicate about external and internal respiration: • gaseous exchange between lungs and blood • transport of respiratory gases from lungs to tissues • gaseous exchange between blood and tissues • transport of respiratory gases from tissues to lungs 8.4 Health Issues Related to the Human Respiratory System 8.4.1 Narrate the effects of Chronic Obstructive Pulmonary Disease (COPD) on the human respiratory system: • asthma • chronic bronchitis • emphysema

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8.1 ICT 8.1 Activity: To study the respiratory structure in insects, frogs and rats

Activity Zone Study the effects of an increase in total surface area on diffusion as an analogy in gaseous exchange.

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Types of Respiratory System Respiratory structures and their adaptations for gaseous exchange

You have learned about respiratory organs and systems in humans and animals in Form 3. The respiratory structure is the respiratory surface that enables gaseous exchange to occur between respiring organism cells and their outer environment. You have also learned in Theme 1, that unicellular organisms such as Amoeba sp. do not need a special respiratory structure because it has a large total surface area to volume ratio for gaseous exchange through diffusion. The ratio of total surface area to volume (TSA/V) depends on the size of the organism. The bigger the size of the organism, the smaller the ratio of total surface area to volume. This means that for large and complex organisms, the volume of the body that requires oxygen will increase more than its total surface area. This explains why large and complex organisms cannot maintain gaseous exchange by diffusion through body surface only. Large organisms require a special respiratory structure for the efficient exchange of gases. How are the respiratory structures of large-sized organisms adapted for efficient exchange of gases? Adaptations of respiratory structures for efficient exchange of gases in big organisms •

Large ratio of total surface area to volume (TSA/V) for the efficient exchange of respiratory gases.



A thin respiratory structure that is one cell thick, allows the diffusion of respiratory gases to occur.



The surface of the respiratory structure is always moist for respiratory gases to dissolve in them.



The respiratory structure is complete with a network of blood capillaries (except for insects), that allows for the efficient delivery of respiratory gases.

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The insect respiratory structure and its adaptations The breathing system of insects is the tracheal system (Figure 8.1). • There are small pores in the thorax and abdomen of insects called spiracles. The spiracle allows the intake of air into the air tube system, which is the tracheal system. • The trachea branches out to form finer tubes called the tracheole. Tracheole is the respiratory surface. The tracheole has the following characteristics that allow for efficient respiratory gaseous exchange. – A large number of tracheoles provides a large total surface area for the exchange of gases. – The tracheole wall is thin and moist. This allows oxygen gas to diffuse into the cells while carbon dioxide quickly diffuses out of the cells into the tracheole. • Some insects have air sacs in their trachea system. This sac is filled with air to speed up the delivery of respiratory gas during active body movements.

air sacs

trachea

oxygen

spiracles

carbon dioxide

CHAPTER 8

tracheole trachea

spiracle body cells

FIGURE 8.1 The tracheal system in a grasshopper

The fish respiratory structure and its adaptations

Brainstorm!

The respiratory structure of fish is the gills (Figure 8.2). The gills are made up of a line of filament that is supported by the gill arch. The following characteristics of filament enable the rapid exchange of respiratory gases.

Why can’t fish gills function if the fish is not in the water?

• The filament has many thin and flat projections called lamella (plural: lamellae). A large number of filaments and lamellae gives a large total surface area for an efficient gaseous exchange process. • The lamella membrane is thin and supplied with many blood capillaries for easy absorption and transport of oxygen and carbon dioxide. PHOTOGRAPH 8.1 Fish gills 8.1.1

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lamella

gills gill arch

gill filaments

FIGURE 8.2 Respiratory structure of a fish

The frog respiratory structure and its adaptations lungs

Skin

skin

In an inactive state, the frog uses its skin for gaseous exchange (Figure 8.3). •

The skin is thin and highly permeable to respiratory gases.



The moist skin allows respiratory gases to dissolve in it.



Beneath the skin, there are many networks of blood capillaries to transport respiratory gases.

Lungs FIGURE 8.3 The respiratory structure of frogs

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The surface of the lungs is folded to increase the total surface area for the exchange of gases (Figure 8.3).



The thin lung membrane eases the diffusion of respiratory gases.



The moist lung walls enable respiratory gases to dissolve in them.



The lungs are also rich with a network of blood capillaries to transport respiratory gases.

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The human respiratory structure and its adaptations

bronchiole

The human respiratory structure is the alveolus which has the alveolus characteristics for efficient respiratory gaseous exchange (Figure 8.4): • A large number of alveoli provides a large total surface area for the diffusion of respiratory gases. • The alveolus wall is always moist. Oxygen and carbon dioxide can dissolve easily, and diffuse through the walls into the blood capillaries. • The alveolus is surrounded by a large network of blood capillaries to hasten the diffusion of respiratory gases. • The thin alveolus wall, that is as thick as one cell, makes the diffusion of gases much easier.

Comparison and contrast of respiratory structures in humans and animals Table 8.1 shows the similarities and differences between the respiratory structures of humans and animals.

blood capillaries

FIGURE 8.4 Alveolus

Similarities • All respiratory structures have a large ratio of total surface area to volume for an efficient exchange of respiratory gases. • All respiratory structures are thin and this makes the diffusion of respiratory gases much faster.

CHAPTER 8

TABLE 8.1 Similarities and differences between the respiratory structures of humans and animals

• All respiratory structures are moist and this allows respiratory gases to dissolve in them. • The respiratory structure is complete with a network of blood capillaries (except insects), that allows for efficient transport of respiratory gases.

Differences Characteristics

Insects

Fish

Respiratory structure

Tracheole

Filament and lamella

How the large ratio of total surface area to volume for the respiratory structure is achieved

Large number of tracheoles

Large number of filaments and lamellae

Formative Practice

2 Explain how the frog skin is adapted for efficient exchange of gases.

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8.1.3

Humans

Skin and lungs

Alveolus

• The surface in the lungs is folded

Large number of alveoli

• Overall skin surface

8.1

1 State the adaptations of the human respiratory structure.

8.1.1

Frogs

3 State the characteristics of tracheoles that help with gaseous exchange in insects. 4 Predict what will happen to a fish if its gills are torn after being caught in a net.

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8.2

Mechanisms of Breathing Humans and animals have different breathing mechanisms. Breathing refers to the repetitive inhalation and exhalation process. The abdominal muscles will contract when air is exhaled. This will increase the air pressure in the trachea and subsequently forces air out of the spiracle.

Breathing mechanism of insects Abdominal muscles that relax and contract enables air to go in and out of the trachea. When inhaling air, the abdominal muscles will relax. This will reduce the air pressure in the trachea and air enters into the trachea through the spiracle.

spiracles

oxygen

carbon dioxide

Breathing mechanism of frogs

ICT 8.2 Video: Breathing mechanism of insects (Accessed on 21 August 2019)

Frogs breathe through the mouth and lungs while in an active state. The sequence of inhalation and exhalation is summarised below. air enters mouth closes

nostrils close glottis closes

nostrils open glottis opens

the floor of the buccopharyngeal cavity is raised

the floor of the buccopharyngeal cavity is lowered

Air is forced into the lungs

Buccopharyngeal cavity is filled with air

Exhalation

Inhalation •



When the frog breathes through the nostrils, the mouth and glottis are closed and the floor of the buccopharyngeal cavity is lowered. The low air pressure in the mouth cavity draws air into the buccopharyngeal cavity through the nostrils.

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glottis opens





Exhalation When the glottis opens, the nostrils close and the floor of the buccopharyngeal cavity is raised.



When the lungs contract, air is expelled from the lungs.



This is helped by the abdominal pressure and the elasticity of the lungs.

The increased air pressure pushes air into the lungs.



Some air is expelled through the nostrils while the rest is mixed with the air in the buccopharyngeal cavity.

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Breathing mechanism of fish The breathing mechanism of fish is aided by its mouth movement and operculum. Ventilation takes place when the fish swims by opening and closing its operculum. This pushes water into the mouth and subsequently through the gills. The ventilation increases the flow of water in the respiratory surface. Dorsal view

INHALATION

EXHALATION

mouth closes

mouth opens

floor of the buccal cavity is lowered

CHAPTER 8

floor of the buccal cavity is raised

gill arch

the operculum water flows opening is out closed

the operculum opening is opened



When the mouth opens, the floor of the buccal cavity is lowered.



When the mouth is closed, the floor of the buccal cavity is raised.



At the same time, the opercular cavity is enlarged and the operculum opening is closed.



Water enters through the gill lamella and gaseous exchange between blood and water occurs through diffusion.



This reduces the pressure in the buccal cavity.





Water from the outside which contains dissolved oxygen enters the mouth.

At the same time, the operculum muscle relaxes and the opercular cavity becomes smaller.



The volume of the buccal cavity is reduced and the pressure in the buccal cavity becomes higher than the pressure outside.



The high pressure causes water to flow through the operculum opening.

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Breathing mechanism of humans The inhalation and exhalation mechanisms of humans are shown in Figure 8.5.

INHALATION

1 2 3 4 5

The external intercostal muscles contract while the internal intercostal muscles relax. This action causes the ribcage to move upwards and outwards.

At the same time, the diaphragm muscles contract and the diaphragm moves downwards to become flat and horizontal. Both mechanisms cause the volume of the thorax cavity to increase and the pressure of the thorax cavity decreases. The higher atmospheric pressure from outside forces air into the lungs.

ribs vertebral column

intercostal muscle

diaphragm

EXHALATION

AR

1 2 3 4 5

The external intercostal muscles relax while the internal intercostal muscles contract. This action causes the ribcage to move downwards and inwards.

At the same time, the diaphragm muscles relax and the diaphragm curves upwards to form a dome. Both movements cause the volume of the thoracic cavity to reduce and the pressure of the thorax cavity to increase. Air is pushed out of the lungs.

FIGURE 8.5 The inhalation and exhalation mechanisms of humans

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Compare and contrast breathing mechanisms in humans and animals What are the similarities and the differences between breathing mechanisms in humans and animals? Table 8.2 explains the comparison between the breathing mechanisms in humans and animals. TABLE 8.2 Comparison between breathing mechanisms in humans and animals

Similarities • Humans and animals have special muscular structures to expand and contract the respiratory cavity. • The breathing mechanism involves changes in the volume and pressure in the respiratory cavity.

Differences between breathing mechanisms of insects, fish, frogs and humans Insects

Fish

Frogs

Humans

Respiratory aperture

Spiracle

Mouth and operculum

Nostrils

Nostrils

Structure that helps breathing

Thorax, abdomen

Operculum and muscular floor of buccal cavity

Muscular buccopharyngeal wall

Diaphragm, ribcage and intercostal muscles

Assisted by the rapid movement of the buccopharyngeal cavity floor and elasticity of the lungs

Assisted by the contraction and relaxation of the intercostal muscles and the diaphragm muscles as well as the movement of the rib cage upward and outward, and downward and inward

Breathing mechanism

Assisted by the contraction and relaxation of abdominal muscles

Formative Practice

Assisted by movements of the floor of the buccal cavity and operculum

8.2

1 State the function of the spiracle in the breathing mechanism of insects. 2 How do abdominal muscles help insects to breathe?

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3 State the two differences between the respiratory mechanisms of fish and humans. 4 Explain the mechanism of inhalation in humans.

CHAPTER 8

Characteristics

Activity Zone Construct a model to show the actions of diaphragm muscles during breathing in humans.

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8.3

Gaseous Exchange in Humans Partial pressure of oxygen and carbon dioxide Gas diffusion depends on the partial pressure difference between two areas. The gas diffuses from an area where its partial pressure is higher to an area where its partial pressure is lower, which is down a partial pressure gradient.

Gaseous exchange and the transport of respiratory gases In the lungs, blood that enters the lung capillaries contains a higher partial pressure of carbon dioxide compared to the alveolus. Carbon dioxide diffuses out carbon dioxide from the lung capillaries and into the alveolus before it is expelled into the atmosphere through the nose and mouth. alveolus The partial pressure of oxygen in the alveolus is higher than the lung capillaries. Oxygen diffuses into the lung capillaries. Oxygen combines with haemoglobin in erythrocytes to form oxyhaemoglobin. oxygen pulmonary vein erythrocytes

lung capillaries

alveolus

pulmonary artery

Blood that enters the lungs through the pulmonary artery has a low partial pressure of oxygen and a high partial pressure of carbon dioxide.

arteriol lung capillary

Blood that leaves the lungs through the pulmonary vein has a high partial pressure of oxygen and a low partial pressure of carbon dioxide. FIGURE 8.6 Gaseous exchange and the transport of respiratory gases in blood circulation

Cellular respiration releases carbon dioxide. The partial pressure of carbon dioxide in cells is higher than tissue capillaries. Carbon dioxide diffuses out from the body cells into the tissue capillaries and is transported back to the lungs.

body cells oxygen

carbon dioxide

When blood reaches the tissue through the tissue capillaries, the partial pressure of oxygen in the blood is higher than that of body cells because cellular respiration uses oxygen. Oxyhaemoglobin breaks down and oxygen diffuses from the tissue capillaries to the body cells. tissue capillary

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Transport of carbon dioxide in the blood circulatory system Carbon dioxide is transported in three ways: • 70% is carried in the form of bicarbonate ion (HCO3—) • 23% carbon dioxide combines with haemoglobin to form carbaminohaemoglobin • 7% is dissolved and carried as carbonic acid (H2CO3)

Brainstorm! Explain why the haemoglobin in foetus has a higher percentage of oxygen saturation compared to haemoglobin in adults.

The transport of carbon dioxide from body cells to tissue capillaries Carbon dioxide (CO2) released by the body cells binds with water (H2O) in the erythrocyte to form carbonic acid (H2CO3).



The carbonic anhydrase enzyme in erythrocyte catalyses this reaction.



Carbonic acid (H2CO3) will break down into bicarbonate ion (HCO3– ) and hydrogen ion (H+).



Then HCO3– diffuses into the blood plasma and is carried to the lungs.

The transport of carbon dioxide from lung capillaries to the alveolus •

When the bicarbonate ion in blood plasma reaches the lung capillaries, it diffuses back into the erythrocyte.



The bicarbonate ion combines again with a hydrogen ion (H+ ) to form carbonic acid (H2CO3).



Carbonic acid ( H2CO3) then breaks down into carbon dioxide and water.



Carbon dioxide diffuses through the lung capillaries into the alveolus and is expelled during exhalation.

Formative Practice

8.3 3 Explain how carbon dioxide is transported from the lung capillaries to the alveolus.

2 In what form is carbon dioxide transported in human blood circulatory system?

4 In what form is oxygen carried to the tissues?

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Atmospheric pressure at sea level is 760 mm Hg. As the atmosphere consists of 21% oxygen (as per volume), the partial pressure of oxygen is 0.21 x 760 mm Hg or 160 mm Hg. This means that the oxygen pressure in the atmospheric pressure is 160 mm Hg. The partial pressure of carbon dioxide at sea level is 0.23 mm Hg.

Brainstorm!

1 What is the value of the partial pressure of oxygen in the atmospheric pressure?

8.3.1

Biological Lens

CHAPTER 8



Explain why exposure to carbon monoxide for a very short period is more dangerous for an individual as compared to exposure to carbon dioxide.

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8.4 Activity Zone Discuss the causal factors and methods of treatment for asthma, chronic bronchitis and emphysema.

Normal bronchiole

Health Issues Related to the Human Respiratory System Chronic Obstructive Pulmonary Disease (COPD) comprises asthma, chronic bronchitis and emphysema. In emphysema, the alveolus loses its elasticity and increases in size. The alveolus wall is damaged, the total surface area of alveolus decreases and the gaseous exchange becomes less efficient. In chronic bronchitis, the bronchiole becomes inflamed, swollen and blocked. This reduces the flow of air and causes difficulties in breathing. A large amount of mucus formed will cause continuous coughing. Damaged cilium causes difficulty in expelling mucus. For an asthmatic patient, the bronchiole walls become swollen and thick. The opening of the bronchiole tube becomes smaller and the air passage becomes narrower. This condition leads to difficulties in breathing and causes breathlessness. Figure 8.7 shows the lungs of a COPD patient. Bronchiole of an asthma patient

inflamed bronchioles in patients generate excessive mucus

normal air passage

Normal bronchiole

air passage narrows bronchiole walls of the patient become swollen and thick

Bronchiole of a chronic bronchitis patient alveolus walls are damaged

bronchiole becomes narrow

FIGURE 8.7 COPD disease

Formative Practice

8.4

Normal alveolus

Alveolus of an emphysema patient

1 What are the effects of chronic bronchitis on the bronchiole?

3 How does the usage of an inhaler help an asthmatic patient to breathe?

2 Explain the condition of bronchiole walls in asthmatic patients.

4 Explain why the gaseous exchange becomes less efficient for an emphysema patient.

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Summary RESPIRATORY SYSTEMS IN HUMANS AND ANIMALS

Types of Respiratory System

• Insects: tracheal system and tracheole • Fish: gill • Amphibian: lungs and moist skin • Human: trachea, bronchus and alveolus

Mechanisms of Breathing

Breathing is the process of inhalation and exhalation

Gaseous Exchange in Humans

Health Issues Related to the Human Respiratory System

Subject to the partial pressure of carbon dioxide and oxygen

Chronic Obstructive Pulmonary Disease (COPD): asthma, chronic bronchitis and emphysema

• Oxygen is transported in the form of oxyhaemoglobin • Carbon dioxide is transported in the form of bicarbonate ion, carbaminohaemoglobin and carbonic acid

Self Reflection Have you mastered the following important concepts? • The respiratory structure in animals and humans

• Respiratory structure adaptations and its function in the exchange of gases • Respiratory structure of humans and animals

• Breathing mechanisms in humans and animals

• Gaseous exchange bet ween lungs and blood and bet ween blood and tissues • Gaseous exchange from lungs to tissues and from tissues to lungs • Health issues related to human respiration

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Summative Practice 8

1 Explain why a transportation system is not required to transport respiratory gases in insects.



2 Why are the lungs of amphibians not as efficient as human lungs?



3 The diaphragm of an individual no longer functions normally due to an accident. Explain how this condition affects the breathing mechanism of the individual.



4 How does an increase in heartbeat rate during an emergency, help a person to face the emergency?



5 (a) (b) (c)



A hardcore smoker can easily suffer from a prolonged cough. Explain how this condition affects the function of the respiratory system. Describe another illness that may be easily contracted by a hardcore smoker. Explain the effects of tar that is present in cigarette smoke on the smoker.



6 One of the effects of emphysema is the loss of elasticity in the alveolus. Explain the effect of this on gaseous exchange.



7 (a) Name structures P and Q that help humans and fish, respectively in gaseous exchange.

P

Q FIGURE 1



(b) (C) (d)

Explain the breathing mechanism of fish. Describe two similarities of structure P and Q that has been adapted to help P and Q function effectively. Give two reasons why the rate of oxygen supply to human cells is faster than the rate of oxygen supply to fish cells if both are of the same size.

Essay Questions

8 The human respiratory systems of humans and grasshoppers have different adaptations to maximise the rate of gaseous exchange. State the similarities and differences between the human respiratory system and the grasshopper breathing system.

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9 (a) Explain how air is inhaled into the lungs. (b) Explain how a carbon dioxide molecule is carried from the body cell to the alveolus to be expelled. Enrichment 10 Air pollution makes breathing difficult in animals and humans. If you are a scientist, which animal will you choose as an indicator of pollution level in a particular area? Explain the justification of your choice. 11 All mammals breathe through the lungs, as with mammals that live in the sea such as whales. How does the whale breathe in water?

Complete answers are available by scanning the QR code provided

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9

CHAPTER

Nutrition and the Human Digestive System 3D food printer

Do You Know...

Can food be designed to meet the nutritional needs of humans?

• What are the str uctural components of the human digestive system? • How is food dig ested and absorbed? • How does food assimilation occur? • How does defaec ation occur? • What is a balance d diet?

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9.2 Digestion 9.2.1 Describe the types of digestion: • physical digestion • chemical digestion 9.2.2 Analyse the process and products of carbohydrate digestion in the mouth. 9.2.3 Analyse the process and products of protein digestion in the stomach. 9.2.4 Describe digestions of carbohydrates, proteins and lipids in the small intestine. 9.2.5 Conduct experiments to study digestions of starch, proteins and lipids in food samples. 9.3 Absorption 9.3.1 Identify the structure of a villus in the ileum. 9.3.2 Communicate about the adaptations of ileum and villus in the absorption of digested food. 9.4 Assimilation 9.4.1 Describe the roles of the circulatory system in the assimilation of digested food. 9.4.2 Discuss the functions of liver in the assimilation of digested food: • metabolism of digested food (carbohydrates and proteins) • storage of nutrients • detoxification

9.5 Defaecation 9.5.1 Explain the functions of the large intestine: • absorption of water and vitamins • formation of faeces 9.6 Balanced Diet 9.6.1 Conduct an experiment to study the energy values in food samples. 9.6.2 Conduct an experiment to determine the contents of vitamin C in fruit or vegetable juices. 9.6.3 Justify the modification of diets for individuals who: • experience obesity • experience a specific disease – diabetes mellitus – cardiovascular – cancer 9.7 Health Issues Related to Digestive System and Eating Habits 9.7.1 Predict the effects of modifying digestive organs on human health. 9.7.2 Outline health issues related to defaecation. 9.7.3 Correlate health issues that are related to eating habits.

CHAPTER 9

9.1 Digestive System 9.1.1 Identify structures of the human digestive system.

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9.1 9.2 salivary gland tongue

Digestive System Structure of the human digestive system The human digestive system is made up of a long and muscular alimentary canal that starts from the mouth to the anus (Figure 9.1). The parts of the alimentary canal include the mouth, oesophagus, stomach, small intestine, large intestine and anus. The other organs in the digestive system are liver, gallbladder and pancreas. Salivary, gastric and intestinal glands secrete digestive juices into the alimentary canal.

Digestion Types of digestion Digestion is the process that breaks down large and complex pieces of food into smaller and simple pieces that can be dissolved for easy absorption. Digestion is made up of two parts, that is, physical digestion and chemical digestion. mouth

pharynx

oesophagus

bile duct

Chemical digestion

The mechanical breakdown of food to form small particles

The decomposition process of complex molecules into simple molecules

Involves chewing and peristalsis

Involves enzymes reaction

Digestion of carbohydrates in the mouth

liver

gallbladder

Physical digestion

stomach

The digestive process begins in the mouth. The presence of food in the mouth stimulates the secretion of saliva from the salivary glands.

pancreas small intestine large intestine

appendix

AR

rectum anus

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FIGURE 9.1 Human digestive system 9.1.1

9.2.1

9.2.2

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Saliva contains salivary amylase that hydrolyses starch to maltose. The pH of the saliva ranges between 6.5–7.5, which is suitable for salivary amylase to act at its optimum. Starch + water

Salivary amylase

maltose

Saliva helps food to form bolus and makes it easier to be swallowed. When swallowing, the epiglottis will close the trachea opening to prevent food from entering the trachea. In the oesophagus, the food bolus is moved by peristalsis. the muscular walls of the Peristalsis is the rhythmic contraction and relaxation oesophagus relax of muscles along the alimentary canal. Peristalsis pushes the bolus through the oesophagus until it enters the stomach (Figure 9.2).

Digestion of protein in the stomach The surface of the stomach wall is lined with epithelial cells that have undergone adaptations in structure and function to form gastric glands (Figure 9.3). These epithelial cells are chief cells, parietal cells and mucous cells. • Chief cells secrete pepsinogen. • Parietal cells secrete hydrochloric acid. • Mucous cells secrete mucus.

the muscular walls of the oesophagus contract

oesophagus

bolus FIGURE 9.2 Peristalsis

Brainstorm! Chew slowly a small piece of bread. Observe the taste when you first started chewing and after a few minutes of chewing. Is there any difference in the taste of the bread?

gastric gland

oesophagus

CHAPTER 9

• •

stomach epithelium

duodenum sphincter FIGURE 9.3 Structure of stomach and gastric gland tissues

mukosa Pepsinogen is an inactive enzyme that is activated by hydrochloric acid to become pepsin. Pepsin then hydrolyses proteins into polypeptides. Protein + water submukosa 9.2.3

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pepsin

mucous cells parietal cells chief cells

polypeptides

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The functions of hydrochloric acid are to: (a) prepare a medium with a suitable pH (pH 1.5–2.0) for pepsin to act (b) stop the enzymatic action of salivary amylase (c) kill bacteria in food The function of mucus is to protect the stomach wall from the reaction of hydrochloric acid and digestive enzymes.

The food in the stomach is mixed with gastric juice made up of hydrochloric acid and pepsin. Food is churned by the peristaltic action of the stomach wall muscles for a few hours. The contents in the stomach finally change to a semifluid called chyme. Chyme enters the duodenum slowly when the sphincter muscle relaxes.

Digestions of carbohydrates, proteins and lipids in the small intestine The small intestine consists of duodenum, jejunum and ileum. Duodenum is the first part of the small intestine which receives chyme from the stomach. Duodenum also receives bile produced by the liver and pancreatic juice secreted by the pancreas (Figure 9.4). liver

PANCREAS

The pancreas secretes pancreatic amylase, trypsin and lipase into the duodenum through the pancreatic duct.

LIVER

• • •





Produces bile The gallbladder stores bile. The bile flows into the duodenum through the bile duct. Functions of bile – neutralise the acidic chyme – prepare an alkali condition (pH 7.6–8.6) for enzyme action in the duodenum – emulsify lipids by breaking down lipids into tiny droplets to increase surface area for lipase activity.

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stomach

bile duct

chyme

gallbladder

pancreas

duodenum

pancreatic duct

FIGURE 9.4 Components that are involved in digestion that take place in the small intestine DUODENUM

• • •

Pancreatic amylase hydrolyses starch to maltose pancreatic amylase Starch + water maltose Trypsin hydrolyses polypeptides into shorter peptides. trypsin Polypeptide + water peptides Lipase hydrolyses lipids into fatty acids and glycerols. Lipid + water lipase fatty acid and glycerol 9.2.4

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Glands on the ileum wall secrete mucus and intestinal juice that contains maltase, sucrase, lactase, lipase and erepsin. The alkali medium in the ileum allows enzymes to act at its optimum. CARBOHYDRATE DIGESTION

• Maltase hydrolyses maltose into glucose. Maltose + water maltase glucose • Sucrase hydrolyses sucrose into glucose and fructose. sucrase Sucrose + water glucose + fructose • Lactase hydrolyses lactose into glucose and galactose. lactase Lactose + water glucose + galactose

Lipase hydrolyses lipids into fatty acids and glycerols. lipase Fatty acids Lipid + glycerol + water PROTEIN DIGESTION

Erepsin hydrolyses peptides into amino acids. Peptides erepsin amino + water acids

Across the fields Chemical digestion involves enzymecatalysed hydrolysis reaction. For example, an enzyme is needed in the decomposition of starch into glucose.

Studying the digestion of starch in a food sample

Problem statement

Hypothesis Amylase hydrolyses starch to a reducing sugar.

Experiment

thermometer thermometer thermometer A B AA BB

What is the effect of amylase on starch? A B

Variables

Video: Processes of digestion, absorption and defaecation (Accessed on 21 August 2019)

CHAPTER 9

tivitcA Activity 1.2sei9.1

ICT 9.1

LIPID DIGESTION

3 ml starch 3 ml of of 1%1% starch suspension + 3 ml suspension + 3 ml of 0.5% amylase of 0.5% amylase solution solution

Manipulated: Presence of amylase Responding: Presence of reducing sugar Fixed: Temperature of water bath at 37˚C, concentration of starch suspension and volume of mixture

3 ml of 1% starch 3 ml of 1% starch suspension + 3 ml suspension + 3 ml of distilled water of distilled water water bath water bath (37 °C) (37 °C) bath water

(37 °C)

Materials 0.5% amylase solution, 1% starch suspension, iodine solution, Benedict’s solution and distilled water

Apparatus Tripod stand, Bunsen burner, wire gauze, 500 ml beaker, test tube holder, thermometer, stopwatch, test tube, dropper, glass rod and measuring cylinder

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Procedure 1 Label 2 test tubes as A and B. 2 Add 3 ml of 1% starch suspension to each test tube. 3 Fill test tube A with 3 ml of 0.5% amylase solution and test tube B with 3 ml of distilled water. 4 Soak both test tubes in a water bath with a temperature of 37 °C for 10 minutes. 5 After 10 minutes, remove 2 ml of the solution from test tube A and put it into a different test tube. Add 3 drops of Benedict’s solution to that test tube and heat the test tube in a boiling water bath for 1 minute. Record the colour of the content. 6 Add 2 drops of iodine solution to the remainder of test tube A. Observe and record the colour of the contents. 7 Repeat steps 5 and 6 for test tube B.

Results Test tube

Contents

A

1% starch suspension + 0.5% amylase solution

B

1% starch suspension + distilled water

Iodine test

Benedict’s test

Discussion 1 Explain the reaction that occurs in test tube A. 2 What is the purpose of preparing test tube B?

Conclusion Is the hypothesis accepted? Suggest a suitable conclusion for this experiment.

Activity

9.2

Studying digestion of protein in a food sample

Experiment

Problem statement What is the effect of pepsin on protein?

Hypothesis Pepsin hydrolyses proteins in the albumen suspension into polypeptides.

Variables Manipulated: Presence of pepsin Responding: Clarity or turbidity of mixture after 20 minutes. Fixed: Temperature at 37˚C, concentration of pepsin solution and dilute hydrochloric acid

Materials Albumen suspension (egg white), 1% pepsin solution, distilled water and 0.1 M dilute hydrochloric acid

Apparatus Test tube, measuring cylinder, 500 ml beaker, water bath at 37 °C, dropper, thermometer and stopwatch.

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Procedure 1 Prepare an apparatus set-up as follows.

Test tube A:

5 ml of albumen suspension + 1 ml of 0.1 M hydrochloric acid + 1 ml 1% pepsin solution

Test tube B:

B + 1 ml of 0.1 M hydrochloric 5 ml of albumenAsuspension acid + 1 ml distilled water

thermometer A

B

2 Soak all test tubes in a water bath at 37 °C. 3 Observe the condition of mixtures in test tubes A and B at the beginning of the experiment and after 20 minutes.

Results

water bath (37 °C)

Clarity or turbidity

Test tube

0 minute

20 minute

A B

Discussion 1 Explain the results achieved in test tube A and B. 2 What is the purpose of adding hydrochloric acid into each test tube?

Conclusion CHAPTER 9

Is the hypothesis accepted? Suggest a suitable conclusion for this experiment.

Activity

9.3

Studying the digestion of lipids in a food sample

Experiment

Problem statement What is the effect of lipase on lipid?

Hypothesis Lipase hydrolyses lipids into fatty acids and glycerols.

Variables Manipulated: Presence of lipase Responding: Time taken for the phenolphthalein indicator to turn from pink to colourless Fixed: Temperature at 37°C, volume of cooking oil and combined volume

Materials Cooking oil, 0.2 M sodium carbonate solution, dishwashing liquid, phenolphthalein indicator, distilled water and lipase

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Apparatus

Two test tubes, test tube rack, water bath at 37 °C, 5 ml and 1 ml syringes, dropper, stopper and stopwatch thermometer

Procedure

A label them B 1 Prepare two test tubes and as A and B.

A

B

2 Fill each test tube A and B with the following: • 2 ml of cooking oil • 1 ml of 0.2 M sodium carbonate solution • 1 ml of dishwashing liquid 3 Close both test tubes with stoppers. Shake both test tubes vigorously after adding the dishwashing liquid.

water bath (37 °C)

4 Add 3 drops of phenolphthalein indicator to each test tube and shake the test tube. 5 Add 1 ml of lipase into test tube A and 1 ml of distilled water into test tube B. 6 Soak both test tubes in a water bath at 37°C. 7 Record the time taken for the phenolphthalein indicator to turn from pink to colourless.

Results Test tube

Contents

A

1 ml of lipase

B

1 ml of distilled water

Time taken for the phenolphthalein indicator to turn from pink to colourless (minute)

Discussion 1 Why is a phenolphthalein indicator used in this experiment? 2 What is the purpose of adding dishwashing liquid into each test tube? 3 Explain the reaction that happens in test tube A. 4 Explain the results obtained in test tube B.

Conclusion Is the hypothesis accepted? State the suitable conclusion for this experiment.

Formative Practice

9.1

1 Explain the importance of the digestion process for humans. 2 Name the structures in the alimentary canal that are involved in food digestion.

4 The small intestine secretes a few types of enzymes to complete the digestion process. Explain how these enzymes complete the digestion process.

3 Name the main cells in the gastric glands and explain the functions of these cells.

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9.3

Absorption The adaptations of ileum and villus in the absorption of digested food Simple molecules produced from the digested food are absorbed in the ileum of the small intestine.

ILEUM

The long ileum is adapted to absorb nutrients because its internal layer is folded and covered by tiny projections called villi (singular: villus) (Figure 9.5).

ileum cross section of a small intestine

villus VILLUS (PLURAL: VILLI)

Villus has the following adaptations to absorb nutrients (Figure 9.5): • The epithelial layer of the villus is one cell thick. This helps accelerate nutrient absorption. • Goblet cells secrete mucus to aid digestion. • The network of blood capillaries helps to transport digestive products to the whole body. • Lacteal carries droplets of fatty acids and glycerol. • The intestinal glands secrete intestinal juices that have digestive enzymes.

epithelial cells blood capillaries

CHAPTER 9

lacteal

lymph vessel

nucleus

microvillus

basement membrane

MICROVILLUS

On the surface of the villus epithelium, there are many tiny projections called microvillus. Microvillus provides a large surface area to increase the rate of nutrient absorption (Figure 9.5). 9.3.1

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mucus goblet cells

FIGURE 9.5 Adaptations of ileum and villi to absorb digested food.

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Absorption of digested food is summarised in Figure 9.6 and Table 9.1. Petunjuk: Glukosa

Indicator:

ICT 9.2

Asid amino Asid lemak Glucose

Video: View inside the small intestine (Accessed on 21 August 2019)

Giserol

lacteal Lakteal

Amino acids

Titisan halus lipid

FattyGalaktosa acids Fruktosa

Glycerol

lacteal

Millennial Career Millennial Career

blood capillaries Kapilari darah

Lipid droplets

A gastroenterologist is a medical specialist who specialises in the human digestive system.

Galactose Fructose FIGURE 9.6 Absorption of digested food TABLE 9.1 Method of food absorption in the ileum

blood capillaries

Activity Zone

Gather information about the absorption of alcohol and drugs.

Absorbed through

Digested food Fructose

Facilitated diffusion

Glucose and galactose

Epithelial cells into blood capillaries

Amino acids Vitamins B and C

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Absorbed with water

Fatty acids and glycerols recombine through the condensation process to form tiny droplets of lipids in the epithelial cells

Simple diffusion Epithelial cells into lacteal Simple diffusion

9.2

2 Name the structure in the villus involved in the transporting of the following nutrients: (b) vitamins A and E

Active transport Osmosis

1 Name the main structures for the absorption of digested food.

(a) amino acids

Active transport

Water

Vitamins A, D, E, K dissolve in the lipid

Formative Practice

Methods of absorption

3 Explain the adaptations of the small intestine to increase the surface area for absorption of nutrients. 4 Explain how the following substances can be transported across the plasma membrane. (a) Glucose, galactose and amino acids (b) Fatty acids and glycerol

9.3.2

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Biological Lens Liver cirrhosis is a type of liver disease caused by factors such as alcoholic drinks, toxic substances and hepatitis. Liver cells are replaced by scarred cells that can cause failure in the liver functions. Hepatitis is an inflammation of the liver caused by viral infection, toxic substances or autoimmune reaction (Photograph 9.1).

The role of the circulatory system The human circulatory system consists of the blood circulation system and the lymphatic system to help transport nutrients to be assimilated. In the assimilation process that occurs in cells, nutrients are used to form complex compounds or structures of components. The blood capillaries in the small intestine combine to form the hepatic portal vein that transports blood to the liver. Lacteals combine to form bigger lymph vessels in the lymphatic system. Then, the contents of the lymph vessels enter the thoracic duct that flows into the left subclavian vein. This lipid is then transported by blood throughout the body.

Functions of liver in the assimilation of digested food The liver is the regulator that controls the quantity of nutrients that enter the blood circulatory system. The liver carries out the following functions. METABOLISM OF DIGESTED FOOD

• •

Glucose is used for cellular respiration. Amino acids are used for synthesising plasma proteins and enzymes. Through the deamination process, excess amino acids are turned into urea to be excreted through the urine.

CHAPTER 9

9.4

Assimilation

DETOXIFICATION

Activity Zone Conduct a research on the various functions of the liver and produce a scrap book

PHOTOGRAPH 9.1 Normal liver and liver of a cirrhosis patient 9.4.1

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• •

Liver cells expel toxic substances from the blood. Toxic substances are expelled through the urine. STORAGE OF NUTRIENTS

Excess glucose is converted to glycogen to be stored.

Normal liver

Liver of a cirrhosis patient

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ASSIMILATION PROCESS IN THE LIVER

AMINO ACIDS

GLUCOSE



The liver synthesises plasma protein and enzymes from amino acids.



Excess amino acids cannot be stored in the body and are broken down through the deamination process to form urea which is then expelled.



When the glucose supply is insufficient, the liver converts amino acids into glucose.



Glucose in the liver is used for cellular respiration when required by the body and the excess is converted to glycogen and stored in the liver.



When the glucose level in the blood decreases and the body needs energy, glycogen is converted to glucose.



When the glycogen supply reaches a maximum level, the excess glucose is converted to fats.

body cell

cellular respiration

liver

amino excess li acids

excess glycogen is stored glucose

synthesis of plasma proteins and enzymes

urea

synthesis of protoplasm (in the cell)

excreted by

hepatic the kidneys portal vein amino acid

glucose

lipid

rol fatty acids + glyce

small intestines carbohydrates

protein

plasma membrane synthesis

FIGURE 9.7 Transportation of nutrients and the assimilation in the liver and cells

lipid

ASSIMILATION PROCESS IN CELLS

AMINO ACIDS •



GLUCOSE

Amino acids are used to synthesise new protoplasm and also repair damaged tissues.





Amino acids are used to synthesise hormones and enzymes.



Glucose is oxidised through cellular respiration to release energy, water and carbon dioxide. Excess glucose is kept as glycogen in muscles. Energy is used for cell processes such as protein synthesis.

Formative Practice

9.3

1 State the meaning of assimilation.

LIPIDS •

Lipids such as phospholipid and cholesterol are the primary components that build the plasma membrane.



Excess fats are kept in adipose tissues found underneath the skin as stored energy.



Fat is oxidised to release energy when there is insufficient glucose.

I understand the difference between p

2 Explain the functions of the liver in the assimilation of digested food.

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9.5 Biological Lens The large intestine has a huge population of bacteria. There are more than 1000 different species of bacteria in the large intestine and a healthy balance between beneficial and less beneficial bacteria is very important for health and a stable environment in the alimentary canal.

Defaecation Functions of the large intestine After the absorption of nutrients is completed in the ileum, undigested food, dead cells, epithelial cells, fibre and water enter the large intestine and move slowly through peristaltic action. Fibre consists of cellulose walls of plant cells. The large intestine carries out two main functions: • absorption of water and vitamins colon • formation of faeces

ABSORPTION OF WATER AND VITAMINS caecum appendix

rectum anus

CHAPTER 9

Substances absorbed are • water and mineral salts • metabolic byproducts of some bacteria such as vitamin B, vitamin K and folic acid.

FIGURE 9.8 Large intestines

FORMATION OF FAECES

After the water is absorbed, the remaining waste is a semisolid called faeces. Faeces contains dead cells from the inner layer of the intestine, waste products such as bile pigments, bacteria and toxic substances. The walls of the large intestine secrete mucus to smoothen the movement of faeces until the anus. The movement of faeces takes about 12 to 24 hours before entering the rectum. The faeces will accumulate in the rectum until the pressure in the rectum increases and triggers the need to expel faeces from the body. The rectum muscles will contract to expel faeces from the anus. This process is called defaecation.



• • •

Brainstorm! What is the effect of antibiotics on the large intestine’s bacterial population? 9.5.1

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Formative Practice

9.4

1 State the main function of the large intestine. 2 What are the substances absorbed in the large intestine?

3 Explain the importance of water absorption and vitamins in the large intestine. 4 Explain the formation process of faeces.

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9.6 Biological Lens

Balanced Diet Energy value in a food sample A balanced diet refers to a diet that consists of all seven food classes (carbohydrates, lipids, proteins, vitamins, mineral salts, fibre and water) in the correct proportion and balanced quantity according to individual needs so that optimal health can be maintained.

1 calorie (cal) = 4.2 joule (J) ENERGY VALUE 1 kilojoule = 1000 joule

Across the fields 4.2 J g-1 °C-1 refers to the specific heat capacity of water, that is, the energy required to increase the temperature of 1 g of water by 1 °C.

sActivity eit1i.v2itcA9.4

• • • •

Energy value is the total amount of energy released when one gram of food is oxidised completely. The energy value in food is measured in the form of heat energy, that is, in kilojoule per gram (kJ g-1). Another unit of heat energy is calorie. 1 calorie or 4.2 joule is defined as the quantity of heat energy needed to raise the temperature of 1 gram water by 1 degree Celsius (°C) at a pressure of 1 standard atmosphere.

• Energy value of food (kJ g-1)

=

Water mass (g) × 4.2 J g-1 °C-1 × Increase in water temperature (°C) Mass of food sample (g) × 1000

Studying the energy value of food samples

Experiment barrier

Problem statement Which food sample has the highest energy value?

Hypothesis Groundnuts have a higher energy value compared to cashew nuts.

thermometer

Variables

cotton wool

Manipulated: Types of food samples Responding: Energy value of food sample Fixed: Water mass

Materials Distilled water, food samples (cashew nuts and groundnuts), cotton wool and plasticine

Apparatus Retort stand with a clamp, thermometer, boiling tube, long needle, electronic weighing scale, barrier, measuring cylinder and Bunsen burner

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retort stand

boiling tube

distilled water food sample needle plasticine

9.6.1

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Procedure 1 Weigh a cashew nut using an electronic weighing scale and record its mass. 2 Measure 20 ml of distilled water using a measuring cylinder and pour it into a boiling tube. 3 Clamp the boiling tube to the retort stand and put in the thermometer. 4 Fix the position of the thermometer using cotton wool. 5 Record the initial temperature of the distilled water. 6 Stick the cashew nut on the needle and hold the needle upright using plasticine. 7 Place the barrier around the apparatus set-up. 8 Light the cashew nut using a Bunsen burner and place it below the boiling tube. 9 Stir the water in the boiling tube slowly and record its highest temperature after the cashew nut has completely burned. 10 Replace the water in the boiling tube. 11 Repeat steps 1 to 9 using groundnuts. 12 Calculate the energy value for each food sample using the following formula: Energy value of = Water mass (g) × 4.2 J g-1 °C–1 × Increase in water temperature (°C) food (kJ g–1) Food sample mass (g) × 1000 13 Record your results in the table below.

Food sample

Food sample mass (g)

Initial temperature of water (°C)

Final temperature of water (°C)

Increase of Temperature (°C)

Energy value of food (kJ g–1)

Cashew nuts

CHAPTER 9

Results

Groundnuts

Discussion 1 Which food sample shows the highest energy value? 2 State two precautionary steps for this experiment. 3 Compare the energy value of food samples obtained from this experiment with their theoretical energy values. Are there any differences? If yes, explain why.

Conclusion Is the hypothesis accepted? Suggest a suitable conclusion for this experiment.

The contents of vitamin C in fruit or vegetables juices The nutrient content in various types of food is different. For example, the vitamin C content in fruits and vegetables are different. 9.6.2

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s1 e.i2 tivit9.5 cA Activity

Determining the contents of vitamin C in fruit juice and vegetable juice.

Experiment

Problem statement Which fruit juice or vegetable juice has the highest content of vitamin C?

Hypothesis Orange juice has the highest content of vitamin C compared to lime juice and carrot juice.

Variables Manipulated: Types of fruit and vegetable juices Response: Volume of fruit juice or vegetable juice needed to decolourise DCPIP solution Fixed: Concentration of DCPIP solution and concentration of an ascorbic acid solution

Materials Orange juice, lime juice and fresh carrot juice, 0.1% ascorbic acid solution, 1% DCPIP solution and distilled water

Apparatus Syringe needles (1 ml and 5 ml), knife, 50 ml beaker, specimen tube, juicer and sieve

Procedure 1 Put 1 ml of 1% DCPIP solution in a specimen tube. 2 Fill the 5 ml syringe needle with a 0.1% ascorbic acid solution. Ensure that there are no air bubbles trapped in it. 3 Insert the tip of the syringe needle into the specimen tube and drip ascorbic acid drop by drop into the DCPIP solution while stirring slowly until the blue colour of the DCPIP solution is decolourised.

ascorbic acid specimen tube

4 Record the volume of the 0.1% ascorbic acid solution needed to decolourise the blue colour of the DCPIP solution.

DCPIP solution

5 Repeat steps 1 to 4 twice to get the average volume for each different juice. 6 Record the volume of each juice in the table below. 7 Calculate the concentration of vitamin C of each juice using the following formula. volume of ascorbic acid solution × 0.1% volume of juice used volume of ascorbic acid solution Vitamin C concentration (mg ml-1) = × 1.0% volume of juice used Percentage of vitamin C =

Results Volume of solution/juice Solution / Juice required to decolourise DCPIP solution (ml) 1 2 3 Average 0.1% ascorbic acid solution Orange juice Lime juice Carrot juice

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Vitamin C concentration (%)

Vitamin C concentration (mg ml-1) 0.1

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Discussion 1 Which juice has the highest content of vitamin C? 2 Why is a 0.1% ascorbic acid solution used as the standard?

Conclusion Is the hypothesis accepted? Suggest a suitable conclusion for this experiment.

One of the factors that affect the loss of vitamin C content is temperature. Therefore, fruit or vegetables must be kept at a suitable temperature range to preserve vitamin C. the effect of temperature on vitamin C in ivitcStudying A Activity 1.2seit9.6 orange juice

Experiment

Problem statement What is the most suitable ambient temperature to keep orange juice?

Hypothesis Orange juice stored at a low ambient temperature has the highest content of vitamin C.

Manipulated: Ambient temperature Responding: Volume of orange juice required to decolourise DCPIP solution Fixed: Volume of DCPIP solution

Materials Oranges, 1% DCPIP solution and ice

CHAPTER 9

Variables Take Note! Ensure that the juice is not exposed too long to avoid oxidation.

Apparatus Specimen tube, knife, syringe needles (1 ml and 5 ml), beakers (50 ml and 100 ml), Bunsen burner, tripod stand, sieve and wire gauze

Procedure 1 Prepare 60 ml of orange juice. 2 Label the beakers A, B and C. Pour 20 ml of orange juice into each beaker. 3 Soak beaker A in ice, leave beaker B at room temperature and soak beaker C in boiling water for 30 minutes. 4 After 30 minutes, determine the vitamin C content in the orange juice as shown in Activity 9.5. 5 Calculate the concentration of vitamin C in the orange juice at each different temperature.

Results Record your results in an appropriate table.

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Discussion 1 Is there a difference in the vitamin C content for the juice at different temperatures? 2 What is the effect of temperature on vitamin C in the orange juice? 3 Based on the results, suggest the best way to ensure that you get a high content of vitamin C from fruit juice or vegetable juice.

Conclusion Is the hypothesis accepted? Suggest a suitable conclusion for this experiment.

Diet modifications for specific individuals A balanced diet for each individual will vary according to lifestyle, health conditions and specific nutritional requirements. Each individual must make wise choices based on a nutrition guide. For example, suggestions for nutritional needs can be made based on Pinggan Sihat Malaysia. Pinggan Sihat Malaysia illustrates the relative quantity of various food classes in a balanced diet (Photograph 9.2). Excessive food intake that is rich in saturated fats can cause health problems such as obesity and cardiovascular diseases. PHOTOGRAPH 9.2 A sample serving based on Pinggan Sihat Malaysia

The cause of obesity Obesity is caused by the storage of excess fats as a result of imbalanced food intake and use of energy.

Millennial Career Millennial Career Nutritionists are specialists in the field of nutrition who advise specific individuals on suitable diets.

Activity Zone Plan meals based on Pinggan Sihat Malaysia for different individuals such as obese individuals, cancer patients and heart patients.

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Effects of obesity Individuals who are obese need to reduce the intake of carbohydrates and fats as well as increase the intake of vegetables and fruits. Otherwise, a diet with excessive saturated fats and high cholesterol may cause diabetes mellitus and various cardiovascular diseases such as atherosclerosis and hypertension which may result in heart attacks (myocardial infarction) or stroke if not treated.

Cancer patients who are undergoing cancer treatment, need to modify their diet to ensure they receive sufficient energy, reduce the risk of infections and enable quick recovery.

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9.7

Health Issues Related to the Digestive System and Eating Habits Adaptation of digestive organs Obesity is a health issue on the rise throughout the world. Although obesity can be controlled through diet management and routine exercise programmes, at times, obesity requires medical treatment. Specialist doctors may suggest surgical procedures to reduce body weight such as gastric bypass (Figure 9.9). A gastric bypass involves a reduction of the stomach size using various methods of surgery. Among the short-term side effects of this surgery are acid reflux, nausea, vomiting, expanded oesophagus, certain food prohibitions and risk of infection. The long-term side effects are dizziness, low blood sugar level, malnutrition, stomach ulcer and defaecation problems.

duodenum

jejunum

gastric sac Part of the stomach that has been bypassed jejunum Part of the duodenum that has been bypassed food digestive juice FIGURE 9.9 Gastric bypass

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The food class that is most important in the defaecation process is fibre. Intake of diet that is high in fibre such as fruits and vegetables can smoothen bowel movements. This can prevent health problems such as constipation, colon cancer, rectum cancer and haemorrhoid. Some of the functions of fibre are to: • stimulate peristalsis • absorb and expel toxic substances • regulate the absorption of glucose especially for diabetes mellitus patients • increase the population of beneficial bacteria in the large intestine Besides, the intake of a large amount of water can ensure that the faeces stay soft and move easily along the large intestine to aid the process of defaecation.

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Health issues related to defaecation

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Health issues related to eating habits Apart from a balanced diet, eating habits also play an important role in fulfilling our energy requirements and maintaining our health. Poor eating habits and an imbalanced diet can cause numerous health problems such as gastritis, muscle dysmorphia, anorexia nervosa and bulimia nervosa. ANOREXIA NERVOSA GASTRITIS

Gastritis refers to the inflammation and corrosion of the stomach epithelial layer by gastric juice when there is no food in the stomach. Untreated gastritis can result in gastric ulcers. The causes of gastritis include eating irregular quantities of food at irregular hours and excessive intake of alcohol or painkillers.

BULIMIA NERVOSA

For people with bulimia nervosa who are also obsessed with controlling their body weight, they will eat a lot and vomit out the food that they have eaten or take laxatives that cause diarrhoea. In the long run, the patient may suffer from dehydration, nutritional problems and eventually cardiovascular disease or kidney failure.

Anorexia nervosa is quite common amongst teenage girls who are obsessed with their body weight. Anorexics will avoid food to achieve their ideal body weight. They also suffer from psychological problems and nutrient deficiency because of their normal digestive system is affected.

MUSCLE DYSMORPHIA

Some individuals feel that their size is small with not enough growth. So, they subject themselves to extreme weightlifting training and exercise. Sometimes, they consume steroids or muscle building supplements. This health issue is called muscle dysmorphia.

Activity Zone Do a case study about the following health issues related eating habits: • diabetes type 2 • obesity • acid reflux • pica

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Formative Practice

9.5

1 In your opinion, why is fibre important in the defaecation process. Explain your answer.

2 Predict the effect of modifying digestive organs such as gastric bypass on human health.

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Summary NUTRITION AND THE HUMAN DIGESTIVE SYSTEM

• Digestion • Absorption • Assimilation • Defaecation

Balanced Diet

• Energy value • Contents of vitamin C in fruit or vegetables juices • Diet modifications for specific individuals

Health Issues Related to the Digestive System and Eating Habits

• The effects of modifying digestive organs on human health • Health issues related to defaecation • Health issues related to eating habits

CHAPTER 9

Digestive System

Self Reflection Have you mastered the following important concepts? • Structure of the human digestive system • Mechanism of digestion • Process and products of carbohydrate digestion in the mouth • Process and products of protein digestion in the stomach • Digestions of carbohydrates, proteins and lipids in the small intestine • Adaptations of ileum and villus in the absorption of digested food • Assimilation of digested food and liver functions • Defaecation • Balanced diet and energy value in food samples • Diet modifications for specific individuals • Health issues related to the digestive system and eating habits

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Summative Practice 9 1 Some people cannot drink milk because it causes diarrhoea and a bloated stomach. Explain why. 2 Amin had some meat dishes for lunch. Explain how the protein is digested in Amin’s stomach. 3 An individual has the following eating habits: Overeating in a short period of time followed by intentional throwing up on purpose after each meal.

Explain how this eating habit can affect the health of this individual.

4 Figure 1 shows the alimentary canal in humans.

Z X

Y

FIGURE 1

(a) Name structures X and Y. (b) (i) The enzymes in X are only effective in an alkaline environment. Explain how an alkaline environment is maintained in X. (ii) Explain how Y is involved in the digestion of carbohydrates in X. (c) Name the enzyme found in Z. Explain how this enzyme functions in the digestion of proteins. (d) A student enjoys eating a lot of oranges. Explain the effect of eating too many oranges on the digestion of starch in X.

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Essay Questions 5 Explain the processes that fat molecules undergo starting from the duodenum until it is finally used by body cells. 6 A teenager had the following for his breakfast. Buttered bread – 2 pieces Hard-boiled eggs – 2

Fresh milk – 1 glass Apple – 1

Explain what happens to the final digested products of his breakfast in his body cells.

7 (a) Explain why a diet rich in fats is not good for health. (b) Suggest suitable types of food for someone who wants to reduce weight and reduce the risk of contracting cardiovascular disease. Explain your answer. (c) Explain the processes of starch digestion, absorption and assimilation in the human body. Enrichment

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8 Medicines in the form of capsules are not broken down in the stomach but absorbed easily by the small intestine. When the blood sample of the patient is taken and analysed, it is found that the molecular structure of this medicine is different from its original molecular structure. Explain why. 9 How are drinks with added artificial sweeteners produced and marketed?

10 Nowadays, many individuals prefer ready-to-eat or frozen food products due to their busy lifestyles. Predict the health risks that may arise if these foods are taken continuously for a long period of time and in large quantities.

Complete answers are available by scanning the QR code provided

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10 CHAPTER

Transport in Humans and Animals

Do you KNOW...

What is a mechanical heart?

• What are the co mponents of the blood circulatory sy stem? • How does the he art pump blood? • How does the lym phatic system return tissue fluids into the blood circulatory system? • What are the he alth issues related to the human circu latory and lymphatic systems?

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10.1 Types of Circulatory System 10.1.1 Justify the necessity of transport systems in complex multicellular organisms. 10.1.2 Identify substances that are transported by the transport system: • substances required by a cell • waste products of a cell 10.1.3 Conceptualise types of circulatory system in complex multicellular organisms. • open circulatory system • closed circulatory system 10.1.4 Compare and contrast circulatory systems in complex multicellular organisms: • insects • fish • amphibians • humans 10.2 Circulatory System of Humans 10.2.1 Describe components of the human circulatory system: • heart • blood vessel • blood 10.2.2 Explain the composition of blood: • blood plasma • blood cells 10.2.3 Compare and contrast the types of blood vessels: • artery • vein • capillary 10.2.4 Label the structure of a human heart and associated blood vessels: • aorta • vena cava • pulmonary artery and pulmonary vein • coronary artery and coronary vein. • semilunar valve • bicuspid valve and tricuspid valve • septum 10.2.5 Describe the functions of parts of the heart. 10.3 Mechanism of Heartbeat 10.3.1 Describe the human heartbeat mechanism: • sinoatrial node (pacemaker) • atrioventricular node • bundle of His • Purkinje fibres 10.3.2 Communicate about forces that cause the blood to circulate in humans: • pumping of the heart • contraction of skeletal muscles

10.4 Mechanism of Blood Clotting 10.4.1 Justify the necessity for blood clotting mechanism. 10.4.2 Describe blood clotting mechanism. 10.4.3 Describe health issues related to blood clotting: • thrombosis • embolism • haemophilia 10.5 Blood Groups of Humans 10.5.1 Describe ABO blood group. 10.5.2 Correlate ABO blood group with blood donation. 10.5.3 Describe the Rhesus factor. 10.5.4 Reason out the incompatibility of Rhesus factor in pregnancies. 10.6 Health Issues Related to the Human Circulatory System 10.6.1 Justify the necessity for a healthy circulatory system. 10.6.2 Communicate about cardiovascular diseases. 10.7 Lymphatic System of Humans 10.7.1 Synthesise the process of formation of tissue fluid and lymph. 10.7.2 Compare and contrast the contents of lymph and: • tissue fluid • blood 10.7.3 Describe components of the lymphatic system: • lymph • lymphatic capillaries • lymphatic vessels• lymph nodes • lymphatic organs 10.7.4 Justify the necessity of the lymphatic system: • complements the blood circulatory system • transports lipid-soluble substances • body defence 10.8 Health Issues Related to the Human Lymphatic System 10.8.1 Describe health issues related to the lymphatic system.

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10.1

Types of Circulatory System The necessity for transport systems in complex multicellular organisms Each living cell requires essential substances such as oxygen and nutrients, and expels cellular waste products such as carbon dioxide and nitrogenous wastes. In Chapter 2, you learned how unicellular organisms such as Amoeba sp. get their essentials and expel wastes by diffusion from and to its external surroundings. Unicellular organisms have a small body mass. Therefore, the total surface area to volume ratio (TSA/V) of the organism is large. As such, Amoeba sp. does not require a specialised transport system to transport substances in and out of the cell. What about multicellular organisms? Can multicellular organisms obtain all essential substances and expel wastes by simple diffusion like unicellular organisms?

Substance exchange can occur by diffusion because the cells are in the environment.

Large complex multicellular organisms cannot obtain essential substances and expel wastes by diffusion because their TSA/V is small. The distance between the external environment and the cell is too far for direct substance exchange. So, how do complex multicellular organisms get essential substances for their cells?

external environment is far away from cells

epidermis

Substance exchange cannot occur by diffusion because the cells are too far away from the environment. body cells FIGURE 10.2 Substance exchange for multicellular organisms

external environment

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FIGURE 10.1 Substance exchange for unicellular organisms

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To address this problem, multicellular organisms have an internal transportation system. In vertebrates, the transportation system is called the blood circulatory system. Before studying further the blood circulatory system, conduct an experiment to study the effects of changes in TSA/V on the diffusion rate.

ICT 10.1 Activity: Studying the effects of changes in total surface area to volume ratio (TSA/V) on the diffusion rate.

Types of circulatory systems in multicellular organisms The circulatory system in multicellular organisms is divided into two types: open circulatory system and closed circulatory system.

• In an open circulatory system, haemolymph flows directly into the body cavity (haemocoel) and bathes the cells. • Haemolymph is a blood-like nutritious liquid found in most invertebrates such as insects and molluscs.

CLOSED CIRCULATORY SYSTEM

• In a closed circulatory system, blood is always contained in a continuous closed blood vessel and is distributed to the whole body. • The exchange of substances that are essential to cells such as oxygen and nutrients occurs across the walls of blood capillaries.

haemolymph haemolymphvessel vessel

blood bloodvessel vessel

haemocoel haemocoel heart heart t t

haemolymph haemolymph

cells cells

heart heart

blood blood

blood bloodcapillary capillary

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OPEN CIRCULATORY SYSTEM

cells cells

open-ended open-endedvessel vessel

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CIRCULATORY SYSTEM OPEN CIRCULATORY SYSTEM Circulatory System of Insects •

Circulatory System of Fish

The circulatory system of insects is an open circulatory system. This means that one or more hearts pump haemolymph through the blood vessels into the haemocoel.



The heart of the fish has two chambers, that is, an atrium (plural: atria) and a ventricle.



Blood that leaves the ventricle is pumped to the gill capillaries to enable gaseous exchange.



Haemolymph flows out from the heart into the haemocoel when the heart contracts.





In the haemocoel, substance exchange between haemolymph and body cells occurs through diffusion.

The gill capillaries carry blood to the blood vessels that transport oxygenated blood to systemic capillaries.





When the heart relaxes, haemolymph flows back into the heart through tiny anterior openings called ostium.

In the systemic capillaries, oxygen diffuses into the tissues while carbon dioxide diffuses from the tissue into the capillaries.



The deoxygenated blood is then returned to the heart atrium through the veins.



As the blood flows in one direction, the fish circulatory system is known as a single circulatory system.

aorta

anterior ostium

aorta aorta aorta

ostium

heart

gill capillaries

posterior

mixed blood

heart

haemocoel

ostium

artery

FIGURE 10.4 The open circulatory system in insects

heart ventricle atrium

posterior FIGURE 10.3 Dorsal view of insect heart

vein

Indicator: oxygenated blood deoxygenated blood mixed blood

mixed blood systemic capillaries FIGURE 10.5 The blood circulatory system of fish

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CLOSED CIRCULATORY SYSTEM Circulatory System of Amphibians •

The heart of an amphibian has three chambers, that is, two atria and a ventricle. Unlike the single circulatory system of fish, blood flows in two directions: pulmocutaneous circulation and systemic circulation. Therefore, this system is known as a double circulatory system. Amphibians are said to have an incomplete double circulatory system because the deoxygenated blood and the oxygenated blood are mixed. Pulmocutaneous circulation transports blood to the lungs and skin, and the exchange of gases takes place here. Systemic circulation transports oxygenated blood to the body tissues and returns the deoxygenated blood to the right atrium through the veins.





1

Deoxygenated blood from body is transported to the right atrium. lung capillaries and skin

2 Oxygenated blood

from lungs and skin is transported by the pulmonary vein to the left atrium.

Circulatory System of Humans •

The human heart consists of four chambers: two atria and two ventricles that are separated completely.



Humans have a double circulatory system. This means that in one complete circulatory cycle, blood flows in the blood vessels through the heart twice. As there are two different circulations, humans are said to have a complete double circulatory system because the deoxygenated blood and the oxygenated blood do not mix.

Pulmonary circulation •

Deoxygenated blood is transported through the pulmonary artery to the lungs for gaseous exchange.



Oxygenated blood from the lungs is returned to the left atrium and flows into the left ventricle. lung capillaries

3 Blood from both

1

4 2 3

right atrium

left atrium ventricle

systemic circulation

pulmonary artery vena cava

right atrium right ventricle

Indicator: oxygenated blood deoxygenated blood mixed blood FIGURE 10.6 The blood circulatory system of amphibians 10.1.4

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aorta pulmonary vein left atrium

left ventricle

systemic capillaries

systemic capillaries 4 The ventricle

then pumps the blood through the pulmocutaneous (lungs and skin) and systemic circulations.

CHAPTER 10

pulmocutaneous circulation

atria enters one ventricle. Although there is some mixing of oxygenated and deoxygenated blood in the ventricle, most of the oxygenated blood remains on the left side of the ventricle while the deoxygenated blood remains on the right side of the ventricle.

Indicator: oxygenated blood deoxygenated blood

Systemic circulation • •

Blood is pumped from the heart to all the body tissues through the aorta. Then the deoxygenated blood returns to the right atrium through vena cava.

FIGURE 10.7 The blood circulatory system of humans

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TABLE 10.1 Similarities and differences between circulatory systems in complex multicellular organisms

Similarities The circulatory system is found in all multicellular organisms. The circulatory system consists of a heart to pump blood or haemolymph (in insects). The circulatory system functions to transport nutrients and wastes. The heart has valves that ensure blood flows in one direction.

Differences Organism

Insects

Fish

Amphibians

Humans

Types of circulatory system

Open blood circulatory system

Closed blood circulatory system

Closed blood circulatory system

Closed blood circulatory system

Single (blood flows in the blood vessel and through the heart once in a complete circulation)

Double (blood flows in the blood vessel and through the heart twice in one complete circulation)

Double (blood flows in the blood vessel and through the heart twice in one complete circulation)

Two (one atrium and one ventricle)

Three (two atria and one ventricle)

Four (two atria and two ventricles)

Incomplete (some oxygenated blood is mixed with the deoxygenated blood in the ventricle)

Complete (oxygenated blood does not mix with deoxygenated blood in the ventricle)

Number of circulations –

Number of heart cavities

The heart is made up of many cavity segments

Separation of oxygenated blood and deoxygenated blood

Formative Practice





10.1

1 State two differences between the circulatory systems of fish and humans. 2 Explain why the blood circulatory system of amphibians is considered as a closed and incomplete blood circulatory system.

3 The flatworm is a multicellular organism. However, the flatworm does not require a specialised transportation system to move substances in and out of the cell. Explain why. 4 Explain why insects need one separate system (the tracheal system) to transport oxygen.

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Malaysian Innovation A group of researchers in Malaysia have produced a device called MyThrob that can be used as a smart examination and monitoring tool for heart diseases. The device studies the original algorithm that can detect abnormal heartbeat and is suitable to be used for monitoring at home.

There are three main components in the circulatory system of humans. • Blood: A type of connective tissue that is made up of blood plasma, blood cells and platelets. Blood acts as a medium of transportation. • Heart: Functions as a muscular pump that circulates blood to the whole body. • Blood vessels: Consist of arteries, capillaries and veins that are connected to the heart, and transport blood to all the body tissues.

Structure of the heart

Do you know that your heart is as big as your fist? The heart is located between the lungs in the thorax cavity and contains four chambers, namely the left atrium, right atrium, left ventricle and right ventricle. The left chamber is separated from the right chamber by a muscular wall called septum. Atrium receives blood that returns to the heart while the ventricle pumps blood out of the heart. The ventricle has thicker walls and contract stronger than the atrium. The muscular wall of the left ventricle is much thicker than the muscular wall of the right ventricle. This is because the left ventricle has to generate greater pressure to pump blood out of the aorta to the whole body while the right ventricle only has to pump blood to the lungs.

CHAPTER 10

10.2

Circulatory System of Humans

Coronary arteries transport oxygenated blood for heart tissues while coronary veins transport deoxygenated blood. arteri koronari coronary arteries

vena koronari coronary veins

TABLE 10.8 The circulatory system of humans 10.2.1

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Aorta is the main blood artery that transports oxygenated blood to the whole body while the vena cava is the main vein that transports deoxygenated blood back to the heart. The semilunar valves at the base of the pulmonary artery and the base of the aorta ensures that blood which flows out of the heart does not flow back into the ventricle when the ventricle relaxes.

The pulmonary artery transports deoxygenated blood from the heart to the lungs while the pulmonary veins transports oxygenated blood from the lungs to the heart.

vena cava

vena kava aorta aorta arteri pulmonari pulmonary artery vena pulmonari pulmonary veins

semilunar valves

atrium kiri left atrium injap bikuspid coronary vein

atrium kanan right atrium injap sabit

bicuspid valve

injap trikuspid coronary artery arteri coronari tricuspid valve

The tricuspid valve ventrikel kanan the (located between right atrium and the right ventricle) ensures that blood which flows into the right ventricle does not flow back into the right atrium. This valve consists of three leaflets.

Brainstorm! What would happen to an individual if the bicuspid valve does not close completely when the ventricle relaxes?

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right ventricle

septum

The bicuspid valve (located between the septum left atrium and the left ventricle) ensures that blood which flows into the left ventricle does not flow back into the left atrium. This valve consists left ventricle of two leaflets.

The septum separates the left part of the heart from the right part of the heart and ensures that the oxygenated blood does not mix with the deoxygenated blood. FIGURE 10.9 Longitudinal section of a human heart

ICT 10.2 Video: Animation of the heart valves (Accessed on 21 August 2019) 10.2.4

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Composition of human blood

Biological Lens

The human blood consists of 55% plasma and 45% cell components. Plasma is the medium of transportation in the body. The components of blood cells consist of red blood cells or erythrocytes, platelets and white blood cells or leucocytes (Photographs 10.1 and 10.2).

Perfluorocarbon (PFC) emulsions can be potentially used as artificial blood. Studies have shown that PFC has the capacity like blood to transport oxygen and carbon dioxide.

erythrocyte

Plasma (forms 55% of the blood volume) Leucocytes and platelets (less than 1% of the blood volume)

platelet

Erythrocytes (forms 45% of the blood volume) leucocyte

PHOTOGRAPH 10.2 Main structural components of blood

CHAPTER 10

PHOTOGRAPH 10.1 Main components of blood

TABLE 10.2 Blood plasma components and the main function of each component

Component

Main function

Water

Blood plasma consists of 90% water. Water is a medium of transportation and a solvent for respiratory gas, ions, digestive products and excretory substances.

Plasma proteins

• Fibrinogen plays a role in blood clotting. • Albumin controls blood osmotic pressure. • Globulin is a type of antibody that is involved in the body’s defence.

Solutes – nutrients such as glucose, excretory substances such as urea and respiratory gas

• Nutrients are important for energy, growth and maintenance of health. • Excretory substances are toxic substances that need to be disposed off from the body. • Oxygen is required in the respiration of cells.

Hormones and enzymes

Hormones control physiological activities in the body. Enzymes are involved in the metabolic processes of cells.

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Table 10.3 shows the characteristics and functions of each blood cell type. TABLE 10.3 Characteristics and functions of blood cell types

Blood cell type Erythrocyte (red blood cell)

side 2.0 view m

pandangan sisi

top view

FIGURE 10.10 Erythrocyte structure

Platelet

Characteristics

Functions

• Has an elastic plasma membrane • The biconcave disc shape enables a large TSA/V for efficient gaseous exchange • It does not have a nucleus at 7.5that m more the mature stage so haemoglobin can be loaded into it pandangan atas in the bone • It is produced marrow of bones such as the sternum and ribs • Can live up to 120 days and is destroyed in the liver or lymph through the phagocytosis process.

• Each erythrocyte has a haemoglobin which is the red pigment that gives blood its red colour. • Haemoglobin contains a heme group. The heme group consists of an iron atom which is the binding site for oxygen. • Haemoglobin combines with oxygen to form oxyhaemoglobin in high oxygen partial pressure conditions. • Oxyhaemoglobin releases oxygen in tissues or cells when the partial pressure of oxygen is low.

• Platelets are produced from fragments or scraps of cell cytoplasm that originate from the bone marrows. • The life span is less than one week.

• Involved in the blood clotting process

FIGURE 10.11 Platelet

Brainstorm! The red blood cell of frogs has a nucleus and is larger than the red blood cell of humans. What are the advantages and disadvantages of nucleated red blood cells?

iron

polypeptide

oxygen

Haemoglobin

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Blood cell type Leucocyte (white blood cell)

Characteristics and functions • • • • • •

The shape is irregular and is not fixed Contains nucleus Does not contain haemoglobin Produced in the bone marrow Life span is less than five days Leucocyte can diffuse out of the capillary pore and fight pathogens in tissue fluids. It is divided into two types: granulocytes (contain granules) and agranulocytes (no granules). • Granulocytes include neutrophils, eosinophils and basophils. Agranulocytes include lymphocytes and monocytes.

L

Granulocytes

E

Neutrophil • The nucleus is made up of two to five lobes. • Ingests bacterial cells and dead cells or tissues from wounds by phagocytosis

U C O

Eosinophil

Basophil

• The nucleus is made up of two lobes. • Releases enzymes that fight inflammation and allergy reaction

• The number of basophils is lowest in the blood • It contains heparin that prevents blood clotting

C Y T E Agranulocyte Lymphocyte • Contains a large nucleus with very little cytoplasm • Produces antibodies to destroy bacteria and viruses that enter the body • Can also produce antitoxins against toxins that are produced by bacteria or viruses

Monocyte • The biggest leucocyte • Spherical-shaped nucleus • Ingests bacteria and dead cells or tissues by phagocytosis

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S

PHOTOGRAPH 10.3 Photomicrograph of leucocytes

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Human blood vessels Blood capillary endothelial cells

endothelium smooth muscle connective tissue

endothelium

smooth muscle connective tissue

Artery

Vein

venule

arteriole

FIGURE 10.12 Relationship between artery, blood capillaries and vein

ARTERY Arteries are blood vessels that transport blood out of the heart. The function of the artery is to quickly transport blood at a high pressure to the tissues. The blood in the artery is under high pressure because of the pumping action of the heart. The aorta is the main artery that leaves the heart. The artery expands when blood is received from the heart. Therefore, the artery wall is elastic to stop it from breaking due to the high-pressured blood that flows through it. The branches of an artery become small vessels known as arterioles when they reach the body tissues. The arteriole continues to branch out and ends at the capillaries. The group of capillaries is called capillary network.

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BLOOD CAPILLARIES Capillaries are blood vessels with thin walls, as thick as one cell. Blood capillaries allow the exchange of gases to occur between blood and cells through diffusion. Nutrients, excretory substances and hormones diffuse through blood capillaries.

VEIN Capillaries rejoin to form larger blood vessels called venules. The venules combine to form veins that transport blood back to the heart. Vena cava is the main vein that carries deoxygenated blood back to the heart. The differences between arteries, capillaries and veins are given in Table 10.4.

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TABLE 10.4 Differences between arteries, capillaries and veins

Characteristics Wall

Artery

Capillaries

Wall is thick, muscular and elastic Arteri

Veins

Wall is as thick as one cell, not muscular and Kapilari not elasticKapilari

Arteri

elastic fibre

Wall is thin, less muscular and less elastic Vena

Vena

wall (as thick as one cell)

Arteri

Kapilari

Vena

lumen

lumen

wall

wall

lumen

Small

Very tiny

Large

Valve

No valve except for semilunar valve at the base of the aorta and at the base of the pulmonary artery

No

Contain valves to maintain one-way flow of blood

Blood pressure

High

Low

Very low

The direction of blood flow

From the heart to the entire body

From the artery to the vein

From the whole body to the heart

lumen (middle space)

CHAPTER 10

Lumen

connective tissues

erythrocyte

PHOTOGRAPH 10.4 Scanning electron microscope shows the cross section of an arteriole (4000x magnification)

Formative Practice

10.2

1 What is the function of the bicuspid valve? 2 Explain why some individuals feel nauseous and faint immediately after donating blood? Why do some blood donors need to take iron pills?

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3 State two differences between the structures of erythrocyte and leucocyte. 4 Explain why the left ventricle has a thicker muscular wall than the right ventricle.

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10.3

Mechanism of Heartbeat How is blood circulated to the whole body? In every contraction, the heart acts as a pump that pumps blood to the whole body. How is every heartbeat triggered and sustained? The heart is made up of cardiac muscles (Photograph 10.5) that intersect and are connected with one another. This arrangement allows electric impulses to spread rapidly through the heart and at the same time, stimulates the cardiac muscle cells to contract simultaneously and uniformly. Cardiac muscles are myogenic. This means that the heart contracts and relaxes without receiving any impulse signal from the nervous system. If the cardiac muscles are stored in a warm oxygenated solution that contains nutrients, these muscles will contract and relax rhythmically on their own.

Blood circulation in humans PHOTOGRAPH 10.5 Cardiac muscle tissue

The produced force that enables blood to circulate in humans is generated by the pumping of the heart and the contraction of the skeletal muscles.

Our World of Biology The “Medtronic Micra” pacemaker is the smallest artificial pacemaker in the world. The size is about the size of a vitamin pill and is placed in the heart without surgery. The artificial pacemaker sends small electrical charges to stimulate heartbeat.

left atrium sinoatrial node

right atrium atrioventricular node

bundle of His left ventricle

right ventricle

Purkinje fibres FIGURE 10.13 The location of sinoatrial node, atrioventricular node, bundle of His and Purkinje fibres

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Pumping of the heart The contraction of the heart is initiated and coordinated by the pacemaker. The pacemaker is a group of specific heart muscle cells that initiates the rate of heart contraction and is located at the right atrium wall (Figure 10.14).

1

The pacemaker generates electrical impulses that spread rapidly through both walls of the atrium and causes the atrium to contract rhythmically. The main pacemaker is called sinoatrial node (SA). The sequence of heart muscle contraction that causes the pumping is shown in Figure 10.14.

The sinoatrial node (SA) generates electrical impulses.

2

sinoatrial nodes (SA nodes)

Electrical impulses spread rapidly in both the atria, causing the atria to contract simultaneously. The contraction of the atria helps to pump blood into the ventricles.

atria

AR

4

The electrical impulses spread from the apex of the heart to the whole ventricle wall. As a result, the ventricles contract to pump blood out to the lungs and body.

atrioventricular node (AV node)

Across the fields

bundle of His

Purkinje fibres

3

The electrical impulses reach the atrioventricular node. The electrical impulses spread through the bundle of His, and the Purkinje fibres up to the apex of the heart.

ventricles CHAPTER 10

Purkinje fibres

Electrical impulses apex of in the heart can the heart be detected by putting electrodes on the skin. The electrocardiogram is a record of the electrical activity that triggers every heartbeat.

FIGURE 10.14 The sequence of heart contraction that causes the pumping of the heart 10.3.2

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During heart pumping, the lub-dub sound can be heard. Do you know what causes this lub-dub sound? The lub-dub sound is the closing sound of the heart valves.

1 tricuspid valve

bicuspid valve

The first ‘lub’ sound is produced when the tricuspid valve and the bicuspid valve close.

2

The second ‘dub’ sound is produced when the semilunar valves close.

FIGURE 10.15 The lub-dub sound of the heart

open valve veins muscle contraction contricts vein closed valve muscles relax

semilunar valves

Contraction of skeletal muscles around the veins The pumping of the heart helps in the distribution and flow of blood through the arteries, arterioles and blood capillaries. However, the force produced by the pumping of the heart is insufficient for the blood flow to continue through the veins and return to the heart. Besides, the blood is forced to flow against the force of gravity. The presence valve in the veins ensures that the blood flows in one direction to the heart. The blood flow in the veins is assisted by: (a) contraction of the smooth muscles found in the venule and vein walls;

FIGURE 10.16 Contraction and relaxation of the foot skeletal muscles

(b) contraction of skeletal muscles around the veins. The contraction of skeletal muscles presses and constricts the veins, causing the valve to open and allow blood to flow towards the heart. The valve is then closed to prevent the blood from flowing back towards the foot (Figure 10.16).

Brainstorm! What would happen to the valve in the blood vessels of our legs if we stand or sit for too long?

Formative Practice

10.3

1 Name the main heart pacemaker.

4 In what circumstances would fingers turn pale?

2 What does the term myogenic mean? 3 Explain why a person who stands too long may faint.

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10.4 STEM Bulletin Scientists have developed a nanomagnetic particle that contains thrombin. This nanoparticle is injected into the injured part to trigger blood clotting and to stop bleeding.

Mechanism of Blood Clotting The necessity for blood clotting mechanism What happens when your finger is injured? Blood will flow from the wound until you apply pressure directly on the wound. The pressure you apply may appear to restrict bleeding temporarily; however, the blood flow is actually stopped by the blood clotting process. Why must the blood clot on the wound? Blood clotting will stop or minimise the loss of blood on the injured blood vessel. Blood clotting also prevents microorganisms such as bacteria from entering the bloodstream through the damaged blood vessel. The blood pressure is also maintained because excessive blood loss will lower blood pressure to a dangerous level. How does blood clotting occur?

Mechanism of blood clotting

CHAPTER 10

Blood clotting involves a series of chemical reactions that takes place in the blood when someone is injured to prevent excessive bleeding.

The coagulated platelets, damaged cells and clotting factors in the blood plasma will form an activator (thrombokinase). Thrombokinase, with the aid of calcium ions and vitamin K, converts prothrombin to thrombin.

Prothrombin (inactive plasma protein)

Fibrinogen (soluble)

TABLE 10.17 Mechanism of blood clotting

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Thrombin (active plasma protein that acts as an enzyme). Thrombin catalyses the conversion of fibrinogen to fibrin.

Fibrin (insoluble) Fibrin is a threadlike protein fibre that forms a network on the wound surface to trap erythrocytes and to close the wound to prevent blood loss.

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Health issues related to blood clotting Under normal conditions, blood does not clot in blood vessels that are not damaged because of some anticoagulants such as heparin. What happens when the blood clotting mechanism of an individual does not function? HAEMOPHILIA

Our World of Biology When you sit for too long, the risk of thrombosis in legs will increase. Make sure that you move your legs once in a while.

Formative Practice

Haemophilia is an example of an illness that prevents blood from clotting.



Haemophilia is a hereditary illness caused by the lack of certain clotting factors in the blood.



Excessive bleeding due to small wounds or bruises can result in death.

THROMBOSIS •

Formation of a blood clot (thrombus).



Thrombosis happens as a result of:



– damage in blood vessels, or

– sluggish blood flow that causes clotting factors to accumulate

Activity Zone Work in groups to collect and interpret information about thrombosis, embolism and haemophilia. Present your findings to the class.



EMBOLISM •

When a blood clot is transported by blood flow, the blood clot is called embolus.



If the embolus gets stuck in a tiny blood vessel, the blood flow will stop.

10.4

1 At the end of the blood clotting mechanism, fibrin will be formed to trap erythrocytes. Explain the meaning of fibrin and its function. 2 Describe two health issues related to blood clotting.

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3 Explain the mechanism of blood clotting. 4 Explain why the formation of blood clots in the blood vessel can cause a heart attack.

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10.5 antigen A anti-B antibody

red blood cell Blood group AB

ood group A

antigen A

tibody

antigen B Blood antigen A group B red blood cell Blood group A

ed blood cell

antigen A no antibodies anti-B antibody red blood cell antigen B anti-A antibody

od group AB

Blood groupcell O red blood

A

antigen B

ood group A

antigen A no antibodies tibody d cell

ed blood cell

od group AB

A

red blood cell Blood group AB no antigens antigen B Blood antigen A group B

Do you know your blood group? Human blood is classified into A, B, AB and O groups. Donation and transfusion of blood is based on the compatibility of the blood group of the donor and the recipient. This is because the recipient has antibodies in the blood serum that Blood group B can act against the antigen on the red blood cells of the donor. Blood red blood cella donor to a recipient must take into consideration transfusion from the blood group type of the donor and the recipient (Table 10.6). If the blood group of both the donor and receiver is not compatible, the red blood cellsB of the recipient will experience agglutination antigen (coagulation). anti-A antibody Blood group O TABLE 10.5 Antigen and antibody in blood groups red blood cell Blood Antigen on red blood cells  Antibody in the blood no antigens group serum Blood group B

A red blood cell Antigen A B anti-A antibodyAntigen B

anti-B antibody

AB

Antigen A and Antigen B

Blood group O red blood cell no antigens

anti-A antibody anti-B antibody FIGURE 10.18 Antigens and antibodies in different blood groups

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10.5.3

Anti-B Anti-A No

O Anti-A and Anti-B antigen B No anti-A antibody TABLE 10.6 Compatibility of blood donor group with the recipient Blood Can donate blood to Blood group O group blood groups red blood cell no A antigens A and AB only

red blood cell anti-A antibody B B and AB only anti-B antibody no antibodies AB anti-A antibody AB only anti-B antibody red blood cell O A, B, AB and O antigen B anti-A antibody

antigen B

no antibodies d cell

ABO blood group

Can receive blood from blood groups A and O only

CHAPTER 10

Blood group A

Blood Groups of Humans

B and O only A, B, AB and O O only

Rhesus Factor Another antigen found on the surface of the red blood cells is the Rhesus factor (Rh factor). The red blood cells of an individual with the Rh factor or antigen D are known as Rh-positive. An individual who does not possess the Rh factor or antigen D is known as Rh-negative. If the blood of a Rh-positive donor mixes with the blood of a Rhnegative recipient, the blood of the recipient will react by producing the Rhesus antibody or anti-D antibody. When the recipient receives another dose of Rh-positive blood, the Rhesus antibody will cause the agglutination of the donor blood cells. This situation could result in the death of the recipient. 185

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Pregnancy and the Rhesus factor

Indicator: Rh-positive Rh-negative Anti-D antibodies

Usually, problems will arise when an Rh-negative mother marries an Rh-positive father and conceives an Rh-positive foetus.

During the last month of pregnancy, fragments of foetal blood cells containing antigen D cross the placenta and enter the blood circulation of the mother. As a result, the white blood cells in the mother’s blood will react and produce anti-D antibodies that will flow back through the placenta into the foetal blood circulatory system.

However, the concentration of antibodies produced is not enough to affect the first child. But the anti-D antibodies will last in the blood circulatory system of the mother.

In a less serious situation, the baby may suffer from anaemia and mental retardation. However, this problem can now be addressed by treating the affected mother with anti-Rhesus globulins after the first pregnancy to stop the formation of anti-D antibodies.

The antibodies will destroy the red blood cells of the Rh-positive baby before or immediately after birth.

Formative Practice

10.5

1 State the blood group which is the universal donor.

The problem arises when the second child is also Rh-positive. The anti-D antibodies that are present in the mother’s blood cross the placenta and destroy the red blood cells of that foetus. The symptoms of this disease are called erythroblastosis fetalis. The second foetus dies if the blood is not replaced with Rh-negative blood through blood transfusion.



The first pair of parents: B and O The second pair of parents: A and B

2 Predict what will happen if the blood group of both recipient and donor is not compatible.



3 Three babies P, Q and R have blood groups B, O and AB respectively. Three pairs of parents have the following blood groups:

4 An Rh-positive male marries an Rh-negative female. The first Rh-positive child is alive but the second child who is also Rh-positive did not survive. Explain why.

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The third pair of parents: AB and O Match the babies with their correct parents.

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10.6 Activity Zone Work in groups and conduct a case study on the practices of maintaining a healthy human circulatory system.

Health Issues Related to the Human Circulatory System The necessity for a healthy circulatory system A healthy circulatory system is important to ensure optimum health. How do we ensure that our circulatory system is healthy? Among the practices for maintaining the circulatory system are a balanced intake of food that is low in fat and regular exercise. The practice of not smoking and not drinking alcoholic drinks also ensures a healthy circulatory system.

Cardiovascular diseases Do you know that cardiovascular diseases are the leading cause of death in our country? Cardiovascular diseases include diseases related to the heart and the blood circulatory system such as atherosclerosis, arteriosclerosis, angina, hypertension, myocardial infarction (heart attack) and stroke. CARDIOVASCULAR DISEASES

Discuss a suitable treatment for heart failure.



Atherosclerosis is the formation and deposition of plaque on the artery walls.



The plaque is formed from cholesterol, lipid, dead muscle tissues and coagulated platelets.



The plaque will clog and narrow the lumen in blood vessels.



The restricted blood flow can cause hypertension.



Hypertension causes fine arteries to break and the patient can suffer from stroke if this happens in the brain.



Stroke is also caused by blood clots (thrombus) that clog the flow of blood in the brain.



Atherosclerosis is the early stage of arteriosclerosis.



Arteriosclerosis occurs when calcium is deposited on the plaque and causes the artery to become hard and lose its elasticity.



If the lumen of the coronary artery (artery for the heart) is narrowed, the insufficient oxygen supply to the heart muscles can cause angina (severe chest pain).



If the artery is completely clogged, myocardial infarction (heart attack) will occur.

CHAPTER 10

Activity Zone

PHOTOGRAPH 10.6 Myocardial infarction (heart attack) 10.6.1

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artery

blood clot restricts the flow of blood

coronary artery

plaque is formed in the artery

dead cardiac muscle tissues

FIGURE 10.19 Formation and deposition of plaque on artery wall

STEM Bulletin Nanotechnology is used in the diagnosis and treatment of atherosclerosis and plaque formation in arteries. In this technique, nanoparticles are designed to resemble high-density lipoprotein cholesterol (HDL) (“good” cholesterol) to help reduce plaque.

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What is the treatment for a patient who suffers from heart failure? What are the risk factors that contribute to cardiovascular diseases and what can we do to ensure that the cardiovascular system is healthy?

Formative Practice

10.6

1 What is the meaning of myocardial infarction? 2 Explain how stroke happens.

3 In your opinion, what are the factors that contribute to an individual’s risk of getting cardiovascular disease? 4 Explain how atherosclerosis happens.

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10.7 1

Human Lymphatic System The formation of tissue fluid

In addition to the blood circulatory system, there is one more system in the body whose function is closely related to the blood circulatory system. This system is called the lymphatic system. The formation of tissue fluid is illustrated in Figure 10.20.

2

Blood that reaches the arterial end of the blood capillary has a high pressure due to the small diameter of capillaries and the pumping force of the heart. blood plasma

This pressure allows the blood plasma to diffuse continuously from the blood capillaries to the intercellular space.

cell

arteriole oxygenated blood at a high pressure

deoxygenated blood at a low pressure

tissue fluid blood capillary

FIGURE 10.20 Exchange of substances between blood capillaries and body cells

3



Blood plasma that occupies the intercellular space and constantly bathes cells is called tissue fluid.



The tissue fluid does not contain any erythrocyte, platelet and plasma protein because these are too large to diffuse out of the blood capillaries.

4



• •

Tissue fluid allows the exchange of materials in the blood and cells to occur. Nutrients and oxygen diffuse from tissue fluid to body cells. Simultaneously, excretory products and carbon dioxide diffuse from body cells to blood capillaries through the tissue fluid.

CHAPTER 10

lymphatic capillary

Lymph formation and components of the lymphatic system At the venule end of the blood capillary, blood plasma is hypertonic compared to the tissue fluid surrounding it. Blood pressure is also lower. As a result, the reabsorption of water, mineral salts and waste takes place in the venule capillary. However, only 85% of the fluid that leaves the blood at the arteriole end of blood capillary diffuses back into the venule end. What happens to the remaining 15% that is left in the intercellular space? This remainder forms about 4 litres of fluid that is lost from capillaries each day. How does the blood circulatory system regain this fluid? 10.7.1

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The lost fluid is collected and returned to the blood through the lymphatic capillary, which is the smallest vessel in the lymphatic system. This fluid is known as lymph and is pale yellow in colour. Table 10.7 and Table 10.8 show the similarities and differences between lymph with tissue fluid and blood. TABLE 10.7 Comparison between lymph and tissue fluid Similarity Both contain plasma without the plasma proteins, erythrocytes and platelets. Differences Lymph

Tissue fluid

Higher content of fat and fat-soluble substances

Low content of fat and fat-soluble substances

High content of lymphocytes

Low content of lymphocytes

TABLE 10.8 Comparison between lymph and blood Similarity Both contain all the contents of plasma such as nutrients, hormones, enzymes, cellular wastes, respiratory gases and leucocytes. Differences Lymph

Blood

Does not contain plasma protein, erythrocyte and platelet

Contains plasma proteins, erythrocytes and platelets

The lymphatic capillary wall consists of one layer of cells only. The lymphatic capillary differs from blood capillary because one of its end is blocked or closed while the other end is connected to the lymphatic vessel (Figure10.21). Lymphatic capillaries found in intercellular spaces merge to form a larger lymphatic vessel. Along the lymphatic vessel, there are lymph nodes at certain distances. lymphatic capillary tissue fluid

cell

arteriole lymph

tissue fluid venule

lymphatic capillary

lymphatic vessel

FIGURE 10.21 Lymph formation

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valve 10.7.2

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The lymphatic system consists of organs such as lymph nodes, spleen, thymus gland, bone marrow, tonsils and appendix (Figure 10.22). The lymphatic system does not have its own pump to circulate the lymph along the lymphatic vessel. The flow of lymph is aided by heartbeat pulse, contraction of skeletal muscles, peristalsis in the digestive tract and changes in pressure during inhalation and exhalation of breath. In the lymphatic vessel, one-way valves ensure the lymph flows continuously to the heart. These valves also prevent the lymph from flowing back.

Relationship between the blood circulatory system and the lymphatic system All lymphatic vessels will eventually join with one of the two main lymphatic vessels which are the thoracic duct dan right lymphatic duct (Figure 10.22). The right lymphatic duct receives lymph from the right hand, chest and right side of the head and neck.

right lymphatic duct

right subclavian vein thymus

The thoracic duct receives lymph from the left side of the head, neck and chest, and all the body parts below the ribs.

tonsils

thoracic duct left subclavian vein bone marrow

spleen

CHAPTER 10

lymphatic vessel

appendix

lymph nodes lymphocyte

lymph node valve

blood vessel tissue fluid

lymphatic capillary FIGURE 10.22 Lymphatic system 10.7.3

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Systemic circulation right subclavian vein

Pulmonary circulation lymphatic capillaries

lymph node

right lymphatic duct lymphatic vessel

pulmonary capillaries

valve vein

The thoracic duct will deliver its contents into the left subclavian vein while the right lymphatic duct will transport lymph into the right subclavian vein. So the lymph collected from the whole body will flow back into the blood circulatory system. Figure 10.23 shows the relationship between the lymphatic system and the blood circulatory system that complement each other.

artery lymph node

systemic capillaries

lymphatic capillaries

FIGURE 10.23 Relationship between lymphatic system and blood circulatory system

The necessity of the lymphatic system The necessity of the lymphatic system is summarised in Figure 10.24. BODY DEFENCE COMPLEMENTS THE BLOOD CIRCULATORY SYSTEM The lymphatic system returns the excess tissue fluid in the intercellular space into the blood flow. The composition, pressure and volume of blood are maintained at a normal range.

Lymph nodes produce and store lymphocytes that are involved in the production of antibodies. NECESSITIES OF THE LYMPHATIC SYSTEM

FIGURE 10.24 The necessity of the lymphatic system

Formative Practice

10.7

1 Name the two main lymphatic vessels. 2 State three main functions of the lymphatic system.

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TRANSPORTATION OF FATSOLUBLE SUBSTANCES Fats and fat-soluble substances diffuse into the lacteal in the villus of the small intestine. Lacteals are lymphatic capillaries. Lipid droplets are transported to the thoracic duct and blood circulatory system through the left subclavian vein.

3 State the differences between the composition of blood plasma, tissue fluid and lymph. 4 After eating fatty food, the number of lipid molecules in the lymph increases by 1%. Explain why. 10.7.4

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10.8 Brainstorm! Why do our legs swell after we sit for too long?

Health Issues Related to the Human Lymphatic System Have you ever wondered what would happen if our lymphatic system does not function properly? What would happen if the excess tissue fluid is not returned to the blood flow? Tissue fluid that is not returned to the blood circulatory system will accumulate in the intercellular space. This will result in the swelling of the body tissues. This condition is known as oedema (Photograph 10.7). Oedema may be caused by a number of factors (Figure 10.25). PARASITIC INFECTION

PREGNANCY The body will produce more body fluid to fulfill the needs of a growing foetus.

DEFICIENCY IN PLASMA PROTEIN Deficiency of albumin in the blood.

PROLONGED BEDRIDDEN PATIENTS Paralysed or stroke patients with limited mobility can suffer from oedema in the legs.



The parasite worm Brugia sp. infects the lymphatic vessel and prevents the flow of lymphatic fluid.



The infected part, for example, leg will swell.



The patient contracts lymphatic filariasis (Photograph 10.8).



This worm is transmitted through mosquito bites.

CHAPTER 10

CAUSES OF OEDEMA

FIGURE 10.25 Causes of oedema normal leg leg with oedema PHOTOGRAPH 10.7 Oedema

Formative Practice

10.8

1 How do parasitic infections happen? 2 Explain what would happen when the tissue fluid fails to return to the blood circulatory system.

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PHOTOGRAPH 10.8 Swollen leg caused by lymphatic filariasis

3 Predict what would happen to the legs of a patient who has been bedridden for a long period of time? Explain your answer. 4 Lipid droplets or fat globules cannot diffuse into the villus blood capillary but must diffuse through the lacteal. Explain why.

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Summary TRANSPORT IN HUMANS AND ANIMALS

Circulatory System

Open Circulatory System Haemolymph flows into the body cavities (haemocoel) and bathes cells Insects One or more hearts pump haemolymph through the haemolymph vessel into the haemocoel

Lymphatic System

Closed Circulatory System Blood is contained in the closed blood vessel that is continuous and is distributed to the whole body Fish The fish heart has two chambers: an atrium and a ventricle Amphibians The heart of an amphibian consists of three chambers: two atria and one ventricle Humans The human heart consists of four chambers: two atria and two ventricles that are completely separated

Circulatory System of Humans • Blood • Heart • Blood vessel

Mechanism of Heartbeat

Mechanism of Blood Clotting Health Issues Related to Blood Clotting • Thrombosis • Embolism • Haemophilia

Components of the lymphatic system • Lymph • Lymphatic capillaries • Lymphatic vessel • Lymph nodes • Lymphatic organs The necessity of the Lymphatic System • Complements the blood circulatory system • Transportation of fatsoluble substances • Body defence Health Issues Related to the Human Lymphatic System • Lymphatic filariasis • Parasitic infection • Deficiency in plasma protein • Pregnancy • Prolonged bedridden patients

Blood Groups of Humans • Blood type A • Blood type B • Blood type AB • Blood type O • Rhesus factor

Health Issues Related to the Human Circulatory System • Arteriosclerosis • Atherosclerosis • Hypertension • Angina • Myocardial infarction • Stroke

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Self Reflection Have you mastered the following important concepts? • The circulatory system in a multicellular organism • Components of the human circulatory system and to compare and contrast the types of blood vessels • Mechanism of the human heartbeat and the generation of force for blood circulation • Mechanism of blood clotting • The ABO blood system and Rhesus factor • Health issues related to the circulatory system • The formation of tissue fluid and lymph • Describe components of the lymphatic system • Health issues related to the lymphatic system

Summative Practice 10 1 An accident victim with blood group B needs an immediate blood transfusion. Is it safe for the patient to receive blood from individuals with the blood group O? Explain why. 2 An individual has a low number of erythrocytes. Explain the effect of this situation on his/her health. Suggest the types of food that should be consumed by the individual to recover from this situation. 3 The human heart has a pacemaker. The heart pacemaker that is damaged can be replaced by an electronic pacemaker. Explain how the electronic pacemaker functions. 4 Name one example of nutrient found in blood and how the nutrient can be transported to cells. 5 One of the lymphatic vessels of an individual is clogged. (a) Explain the effects on the lymphatic system of the individual. (b) Explain what will happen if the lymphatic vessel in the leg is clogged?

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6 Figure 1(a) shows a schematic of the blood circulatory system in humans and Figure 1(b) shows the schematic of the blood circulatory system in fish.







Head, neck, arm

HEART

Lungs

HEART

Body

Gills

(b) Body (a) (a) (b) (c) (d)

FIGURE 1

Explain the blood circulatory system of fish. Based on Figure 1, compare the human and fish blood circulatory system. Explain the similarities between the two blood circulatory systems. Why does the blood flow in fish encounter more obstacles compared to the blood flow in humans and explain how the fish can overcome this problem?

Essay Questions 7 Coronary heart disease is the main cause of death in our country. The following factors can increase the risk of an individual contracting this disease: • smoking • unbalanced diet • unhealthy lifestyle Explain how these factors can contribute to coronary heart disease. 8 (a) Explain how the rhythmic contraction of heart muscles occurs. (b) Ali’s leg feels numb after sitting cross-legged for an hour. Suggest the action to be taken and give your reasons. (c) Elly enjoys eating beef rendang and nasi lemak. Explain why this practice of eating in the long term can affect her health.

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Enrichment 9 (a) A baby is born with a damaged bicuspid valve which cannot close tightly. Explain the effect of this condition on the baby. (b) A normal baby has a thick muscular heart wall that separates the left heart from the right heart. If this muscle is not formed completely, predict the outcome on the quality of blood that flows into the aorta. 10 How should an individual with a coronary artery that is clogged with cholesterol deposits be treated? 11 Each year, thousands of people die from excessive blood loss caused by injuries during accidents or war. One way to reduce the continuous outflow of blood from the injury is to apply pressure on the wound with a bandage. In your opinion, what adaptations can be done to the bandage to make it more efficient in stopping blood loss temporarily until the patient is admitted to the hospital?

Complete answers are available by scanning the QR code provided

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11 CHAPTER

Immunity in Humans

Do you KNOW...

How do our bodies fight bacteria and viral infections?

• What are the th ree lines of body defence in hu mans? • How do antibod ies react with antigens? • What are the typ es of immunity in human s?

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11.1 Body Defence 11.1.1 Define: • immunity • antigen • antibody 11.1.2 Describe the three lines of body defence in humans: • the first line of defence: – physical – chemical • the second line of defence: – fever – inflammation – phagocytosis • the third line of defence: – antibody – memory cell 11.2 Actions of Antibodies 11.2.1 Discuss the actions of antibodies on foreign antigens: • neutralisation • agglutination • precipitation • opsonisation • lysis 11.3 Types of Immunity 11.3.1 Communicate about the types of immunity: • passive immunity • active immunity 11.3.2 Compare and contrast passive immunity and active immunity 11.4 Health Issues Related to Immunity 11.4.1 Describe health issues related to Acquired Immuno Deficiency Syndrome (AIDS).

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11.1

Body Defence You may recall learning about the body defence system in Form 2. The body defence system reacts when pathogens infect the body. A pathogen is a microorganism that causes diseases. Examples of pathogens include bacteria (singular: bacterium), viruses and parasites. Pathogens can only cause diseases if they successfully infect body cells. The body defence system recognises pathogens as foreign particles known as antigens. Antigens are foreign particles that enter the body and subsequently stimulate the immune response. Antigens stimulate the lymphocytes to produce antibodies into the blood flow to destroy the antigens. Antibodies are proteins found on the lymphocyte surface or proteins released by lymphocytes into the blood plasma. The interaction between antibodies and antigens that cause antigens to be destroyed is called the immune response (Figure 11.1).

antibody antigen

Immunity is the body’s ability to fight infections caused by pathogens or other foreign objects, through specific attacks on the pathogens. When our body can fight a disease, we are said to be immune to that disease. There are three lines of defence to fight against diseases in our body: • The first line of defence • The second line of defence • The third line of defence

The first line of defence The first line of defence consists of the physical and chemical line-up FIGURE 11.1 Interaction between antibodies and that prevent pathogens from entering antigens the body. The first line of defence is the defence line that is not specific and acts to prevent pathogens from entering the body. Figure 11.2 shows the organs and mechanisms involved in the first line Activity Zone of defence. List the physical and chemical defences found in the first line of defence.

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11.1.1

11.1.2

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LYSOZYME Lysozyme found in the secretion of tears, nasal mucus and saliva, is an antimicrobial protein that can dissolve and destroy some types of bacteria.

MUCOUS MEMBRANE The mucous membrane that lines the respiratory tract secretes a sticky fluid called mucus. Mucus contains lysozyme that destroys bacteria found in the air that enters the respiratory system.

MECHANISM OF BLOOD CLOTTING The blood clotting mechanism prevents bacteria from entering through wounds.

HYDROCHLORIC ACID

CHAPTER 11

Hydrochloric acid in the stomach destroys bacteria present in food and drinks.

FIGURE 11.2 The first line of defence

SKIN • It is the physical defence that prevents the entry of pathogens because it is tough and is difficult for microorganisms to penetrate. • The continuous shedding of dead cell layers on the skin surface makes it difficult for various types of microorganism to grow. • Acts as a chemical shield through the secretion of sebum. Oil and acid in the sebum prevent the growth of various types of microorganisms. • Sweat secreted by the skin contains lysozyme, a type of enzyme that breaks down the cell wall of some bacteria. 11.1.2

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PHOTOGRAPH 11.1 The electron micrograph shows a phagocyte extending its pseudopodium to engulf bacteria

The second line of defence

• The second line of defence is fever, phagocytosis and inflammation. • The mechanism of the second line of defence is also not specific. Fever Fever is the second line of defence mechanism that fights infections. Fever increases phagocytic activity and fights against microorganisms that infect the body. Phagocytosis • The phagocyte is a leucocyte that can carry out phagocytosis. Neutrophils and monocytes are phagocytes. • Phagocytosis is the process by which microorganisms or other particles such as dead cells are trapped and digested by phagocytes. • When an infection occurs, the phagocytes move to the infected area and enter the tissue fluid through the pores of the capillary wall. • When a phagocyte encounters a pathogen, the phagocyte will engulf the pathogen and the lysozyme in the phagocyte will digest the pathogen (Photograph 11.1). • The stages of phagocytosis are summarised in Figure 11.3. the bacterium and envelops the 1 towards bacteria Phagocyte extends its pseudopodium

bacterium

ingestion 2 Bacterial forms phagosome

ICT 11.1 Video: Phagocytosis (Accessed on 21 August 2019)

lysosome

phagosome

combines with 3 Phagosome lysosome that secretes lysozyme

phagocyte

into the phagosome

phagolysosome lysozyme destroyed by the 4 islysozyme

Bacterium in the phagosome bacterium decomposes

Phagocyte expels the 5 remains of the digested microorganism out of the cell

FIGURE 11.3 The phagocytosis stages

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11.1.2

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Inflammation Inflammation is the immediate response that destroys and neutralises harmful actions of microorganisms and toxins at the early stages of infection. The inflamed area will swell, turn red and feel painful. The response to inflammation is described in Figure 11.4. skin

Biological Lens Pus is a combination of microorganisms, fragments of tissues and white blood cells that can be found in seriously infected areas or damaged tissues.

infected area

1 The damaged tissue releases

histamine. Histamine will stimulate an immediate inflammatory response. 2 • Histamine will cause the blood

bacterium

capillaries to expand for more blood to flow to the infected area.

4

• Histamine also increases the permeability of blood capillaries to phagocytes. • The phagocytes and clotting factors will accumulate in the infected area.

The phagocytes carry out phagocytosis.

phagocyte histamine platelets

3 The blood clotting

mechanism is triggered.

antigens antigen receptor site

FIGURE 11.4 Inflammatory response antibody

If pathogens overcome the second line of defence, the third line of defence will be activated. The third line of defence is the immune response of the lymphocytes. • The lymphocytes formed in the lymph nodes produce antibodies. • The actions of antibodies are specific. Each type of antibody can only combine with a certain type of antigen (Figure 11.5). • When a person is infected with pathogens, a large number of lymphocytes will accumulate in the lymph nodes to destroy the antigens and foreign particles. This will cause the lymph nodes to swell. • The lymph nodes also contain macrophages that destroy bacteria, dead tissues and foreign particles through phagocytosis. • Lymphocytes are divided into two types, T lymphocytes and B lymphocytes. • The T lymphocyte attacks cells infected by pathogens. T lymphocytes stimulate B lymphocytes to produce memory cells. • If the same pathogen attacks, the memory cells will be stimulated to produce antibodies immediately. 11.1.2

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CHAPTER 11

The third line of defence

lymphocyte

FIGURE 11.5 The antigen molecule will combine with the antigen receptor site found in the antibody molecule

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Formative Practice

11.1

1 What is the meaning of immunity? 2 Name two characteristics of the skin that allows the skin to react as an effective first line of defence.

11.2

3 How does the phagocyte destroy pathogens that have penetrated the first line of defence? 4 Differentiate between antigens and antibodies.

Actions of Antibodies Antigens are destroyed by antibodies through several mechanisms as illustrated in Figure 11.6.

AGGLUTINATION

antibody

Antibodies coagulate the pathogens and make them an easy target to be trapped and destroyed by phagocytes.

antibody

toxin

antigen

NEUTRALISATION Antibodies bind with toxins produced by bacteria and neutralise the toxin.

precipitation of antigen molecules

PRECIPITATION Antibodies react with dissolved antigens to form an insoluble complex (precipitate) that is easily destroyed by phagocytes.

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antibody

11.2.1

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bacterium

antigen bacterium

OPSONISATION

antigen

Antibodies combine with antigens and act as a marker for phagocytes to recognise the antigens and destroy them.

antibody

gen opsonin antibodies combine with antigens

LYSIS Antibodies combine with antigens and cause bacteria to be broken down and decomposed.

nucleus

lysine antibody combines with antigen phagocyte traps the bacterium that has been identified by the antibody marker

baterium

antigen bacterium undergoes lysis (decomposition) FIGURE 11.6 Action of antibodies on antigens

Our World of Biology The Ministry of Health (MOH) recommends that babies aged 2 to 3 months be immunised against diseases such as diphtheria, pertussis, tetanus, poliomyelitis and meningitis.

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There are two types of immunity: active immunity and passive immunity. Active immunity means that lymphocytes produce their own antibodies as a response to stimulation by the antigens. Passive immunity means that the body receives antibodies from an external source. Both of these types of immunities can be naturally or artificially acquired.

CHAPTER 11

11.3

Types of Immunity

IMMUNITY

ACTIVE IMMUNITY •

Natural active immunity Acquired after an individual recovers from an infection



Artificial active immunity Acquired when an individual is given a vaccine injection

PASSIVE IMMUNITY •

Natural passive immunity Acquired through breastfeeding and from the mother to the foetus during pregnancy



Artificial passive immunity Acquired through an antiserum injection

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Active immunity and passive immunity Brainstorm! Why are only female pupils given the HPV vaccination (Human papillomavirus)?

Let us examine active immunity and passive immunity in greater detail. ACTIVE IMMUNITY •

Antibodies are produced naturally by lymphocytes.



Active immunity remains for a long period of time.

NATURAL ACTIVE IMMUNITY

ARTIFICIAL ACTIVE IMMUNITY



When someone is infected by pathogens, lymphocytes will produce antibodies as a response to these antigens.



To protect oneself from being infected by a highly infectious disease, an individual can be immunised against the disease.



When an individual recovers from an infection, that individual will gain a permanent immunity against the disease.



Immunisation refers to the process that stimulates immunity against a specific disease through vaccine injections.



When the individual is attacked again by the same pathogen, the lymphocytes that stored memories of the pathogen, that is, memory cells will rapidly produce antibodies to react immediately against the antigens.



Vaccine is a suspension of pathogens that are weakened, dead or non-virulent.



When a vaccine is injected into the body, the vaccine will stimulate lymphocytes to produce antibodies to fight the pathogens.



The first vaccine injection will usually result in a low level of antibody production which is insufficient to protect an individual from the disease. A booster dose must be administered to increase the antibody production to a level of immunity that can protect the individual from the disease.



If the individual is infected by actual pathogens, the lymphocytes will produce enough antibodies and immediately destroy these pathogens.



Examples of vaccines are the Salk vaccine for poliomyelitis, BCG vaccine (Bacille Calmette-Guerin) for tuberculosis (TB) and HPV vaccine for cervical cancer.

PHOTOGRAPH 11.2 An individual who has recovered from chickenpox or influenza has gained a natural active immunity

PHOTOGRAPH 11.3 Immunisation protects a person from being infected by infectious diseases

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PASSIVE IMMUNITY •

The body does not produce its own antibodies.



Antibodies are obtained from an external source.



Passive immunity does not persist and can only give immediate, shortterm and temporary protection.

NATURAL PASSIVE IMMUNITY

ARTIFICIAL PASSIVE IMMUNITY



This immunity is acquired by a foetus when the mother’s antibodies diffuse through the placenta into the blood flow of the foetus.



This immunity is acquired through an antiserum injection or serum that contains specific antibodies to fight specific antigens.



Antibodies also protect the baby for the first few months after birth through antibodies that are found in the mother’s milk or colostrum when breastfeeding.



The antiserum injection gives immediate protection but only for a short period of time.



Examples of antiserum are antitetanus, anti-rabies and antiserum for poisonous snakes.

Tetanus toxoid suspension

PHOTOGRAPH 11.4 Babies gain natural passive immunity from the mother’s milk

CHAPTER 11

Injected in a horse

The antitetanus from the horse serum is concentrated and purified

Injected into individuals with high risk of tetanus

FIGURE 11.7 Antitetanus preparation 11.3.1

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The individual is protected from tetanus infection

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TABLE 11.1 Comparison between artificial active immunity and artificial passive immunity

Similarities • Protects the body from infectious diseases • Involves interaction between antibodies and antigens

Differences Aspect

Artificial Active Immunity

Artificial Passive Immunity

Acquired through

Vaccine injection

Antiserum injection

Injected substance

Vaccine is a suspension of pathogens that are weakened, dead or non-virulent.

Antiserum is a serum that contains specific antibodies.

Purpose

Prevention

Treatment or when immediate protection is required

Effect

Does not give immediate protection

Gives immediate protection

Immunity period

Immunity lasts for a long period of time

Immunity is temporary and does not persist

When injection is given

Vaccine injection is administered before being infected

Antibody injection is given in advance if there is a high risk of infection or immediately after being infected by a disease

Antibody

Antibodies are produced by the lymphocytes

Antibodies are obtained from antiserums

The need to give a second injection (booster dose)

Must be given to boost the level of antibodies above the level of immunity as a protection against the disease

Is only given when the antibody level in the blood drops below the level of immunity and the patient is still infected by the disease

antibody level in blood (arbitrary units)

the immunity level refers to the concentration of antibodies that is sufficient to fight the disease

60

60

level of immunity

40 20 0

2

4

6

8

time (month)

first second injection injection

FIGURE 11.8 The antibody level in the blood of a person after the first and second vaccinations

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antibody level in blood (arbitrary units)

level of immunity

40 20 0

2 first injection

4

6

8

time (month)

second injection

FIGURE 11.9 The antibody level in the blood of a person after the first and second antiserum injections

11.3.2

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11.2

1 What are the types of immunity that decrease according to time? Explain why. 2 Propose immediate treatment that can be given to someone who has been bitten by a poisonous snake.

11.4 Biological Lens HIV is able to mutate and change the cell structure when it spreads. This gives the virus a high resistance to drug therapy.

Millennial Career Millennial Career Immunologists are specialists in allergy diseases and diseases that involve the immune system.

3 State one difference between artificial passive immunity and artificial active immunity. 4 In your opinion, why must we follow and complete the immunisation plan in Malaysia?

Health Issues Related to Human Immunity Acquired Immunodeficiency Syndrome (AIDS) The human immunodeficiency virus (HIV) is a virus that attacks the human immune system. HIV infection causes Acquired Immunodeficiency Syndrome (AIDS). An AIDS patient is easily infected by other diseases because of the progressive destruction of the individual’s immune system. HIV spreads in the lymphocyte and destroys the lymphocyte (Photograph 11.5). An individual infected with HIV does not show any symptoms for the first few years although HIV has been actively attacking the immune system. Symptoms of the disease include chronic diarrhoea and fungi infection which are only visible after 8 to 10 years. Since the immune system of the individual is already weakened, the body can be easily infected by diseases. Finally, the immune system is paralysed and the patient will die from other infections.

CHAPTER 11

Formative Practice

HIV transmission HIV enters the body through the transfer of body fluids such as blood and semen or across the placenta. Women infected with HIV can transfer the virus to the baby during pregnancy, birth or breastfeeding.

lymphocyte HIV

PHOTOGRAPH 11.5 HIV attacks lymphocyte 11.4.1

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Nevertheless, HIV infection in the foetus and newborn baby can be avoided with proper medical treatment when the mother is pregnant and during birth. Individuals can be infected by HIV through unprotected sexual relations with an infected individual. They can also be infected when they share contaminated needles used to inject drugs or tattoo ink. In addition, HIV is also spread through HIV-infected blood transfusion. There are a few types of diseases and conditions related to the immune system. Conduct the following research study activity to find out more.

ivitcA Activity 1.2seit11.1

Conducting a research study on issues related to the human immune system

Research study

Materials Medical magazines and the Internet

Procedure 1 Conduct a research study with a friend on: • Systemic Lupus Erythematosus (SLE)

• Allergy

2 Discuss your findings with friends from other groups and present the findings of each group.

Formative Practice

11.3

1 What is the meaning of AIDS? 2 Explain how HIV infection can cause someone to suffer from AIDS.

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3 Why is a person who is infected with HIV, may not necessarily suffer from AIDS? 4 How can AIDS be prevented?

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Summary IMMUNITY IN HUMANS

Body Defence The first line of defence • Physical – Skin • Chemical – Sebum – Sweat – Lysozyme – Mucous membrane – Hydrochloric acid – Mechanism of blood clotting The second line of defence • Fever • Inflammation • Phagocytosis The third line of defence • Antibody • Memory cell

Actions of Antibodies

• Neutralisation • Agglutination • Precipitation • Opsonisation • Lysis

Types of Immunity

Health Issues Related to Human Immunity • Acquired Immunodeficiency Syndrome (AIDS) • Systemic Lupus Erythematosus (SLE) • Allergy

Active immunity • Active natural immunity (when someone is infected by pathogens, lymphocytes will produce antibodies as a response to the antigen) • Artificial active immunity (a process that stimulates immunity through vaccine injection) Passive immunity • Passive natural immunity (acquired by the foetus in the mother’s womb and during breastfeeding) • Artificial passive immunity (serum injection that contains antibodies that fight against certain antigens)

Self Reflection Have you mastered the following important concepts?

• Definition of immunity, antigen and antibodies • The first, second and third lines of defence in a human body • Antibody action on antigen • Active and passive immunities

• Health issues related to human immunity

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Summative Practice 11 1 Suggest an immediate treatment to an individual bitten by a very poisonous snake. 2 Explain how a mother who has HIV can infect a foetus in her womb.

3 (a) State the type of immunity a foetus receives from its mother. (b) Explain how the placenta helps in the immune system of the foetus. 4 Figure 1 illustrates the changes in the antibody levels in the blood of individuals X and Y for a specific period of time.

the antibody level level the antibody

the antibody the antibody level level in blood in blood

in blood in blood

first injection first injection

of immunity level oflevel immunity

of immunity level oflevel immunity

time time (weeks) (weeks)

time time (weeks) (weeks) first injection first injection

Individual X Individual X

Individual Y Individual Y

FIGURE 1

(a) (i) What type of immunity did individuals X and Y acquire? (ii) State the substance injected in individuals X and Y. (iii) Explain the differences in the content of the substances you mentioned in (a)(ii). (b) (i) On the graph curves of individuals X and Y, mark with an arrow, the time of the second injection is given. (ii) Why do individuals X and Y need a second injection? (iii) Based on the graph curves for individuals X and Y, state two differences in the immunity achieved by individuals X and Y.

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Essay Questions 5 Two individuals acquired immunity against chickenpox in different situations. Individual X recovered from chickenpox. Individual Y was injected with a type of suspension and received immunity against chickenpox after a few months. Explain the immunity acquired by (a) individual X (b) individual Y 6 (a) A newborn baby needs to receive immunisation based on the Immunisation Plan recommended by the World Health Organisation (WHO). Explain why the immunisation programme is required. (b) (i) Some vaccine injections require only one dose throughout the lifetime of an individual. Explain why. (ii) Sinti’s mother forgot to bring Sinti to the clinic for the third dosage of the hepatitis vaccination. Explain the effects on Sinti’s immunity. (iii) Aziman accidentally stepped on a rusty nail during a mountain climbing expedition. Describe the type of injection that is suitable to be administered by the doctor. Explain your answer. (c) Explain how HIV can paralyse the immune system of a person infected by the virus. Enrichment 7 Sometimes doctors prescribe antibiotics to treat some infectious diseases. Doctors will advise taking all the antibiotics prescribed for the recommended period. Explain why it is important to follow this step. 8 You visited a sick friend in a hospital. MRSA (methicillin-resistant Staphylococcus aureus) is a strain of bacteria that is usually found in hospitals. This bacterial strain is immune to many types of antibiotics due to the numerous types of antibiotics used to treat patients in the hospital. Suggest steps that you can take to prevent the infection of MRSA.

Complete answers are available by scanning the QR code provided

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12 CHAPTER

Coordination and Response in Humans

Can robots function fully like humans in the future? Sophia Robot

12.1 Coordination and Response 12.1.1 Make a sequence and describe the components in human coordination: • stimulus • effector • receptor • response • integration centre 12.1.2 Identify and describe external and internal stimuli.

12.1.3 List the types of sensory receptors based on the stimuli involved: • chemoreceptor • mechanoreceptor • photoreceptor • thermoreceptor • baroreceptor • nociceptor 12.1.4 Justify the necessity to respond to external and internal stimuli.

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12.2 Nervous System 12.2.1 Construct an organisational chart and explain the structures of the human nervous system: • central nervous system – brain – spinal cord • peripheral nervous system – sensory receptor – cranial nerve – spinal nerve 12.2.2 Explain the functions of parts of the central nervous system related to coordination and response: • brain – cerebrum – hypothalamus – cerebellum – pituitary gland – medulla oblongata • spinal cord 12.2.3 Communicate about the functions of parts of the peripheral nervous system in coordination and response. 12.3 Neurones and Synapse 12.3.1 Draw and label structures of a sensory neurone and a motor neurone: • dendrite • myelin sheath • axon • node of Ranvier • cell body 12.3.2 Analyse the functions of each type of neurone in impulse transmission. 12.3.3 Explain the structure and function of synapse. 12.3.4 Explain the transmission of impulse across a synapse. 12.4 Voluntary and Involuntary Actions 12.4.1 Compare and contrast voluntary and involuntary actions. 12.4.2 Describe the reflex actions involving: • two neurones • three neurones 12.4.3 Draw a reflex arc. 12.5 Health Issues Related to the Nervous System 12.5.1 Communicate about the health issues related to the nervous system.

12.5.2 Describe the effects of drug and alcohol abuse on human coordination and response. 12.6 Endocrine System 12.6.1 State the role of endocrine glands in humans. 12.6.2 Identify and label the endocrine glands in humans. 12.6.3 Analyse the functions of hormones secreted by each endocrine glands: • hypothalamus – gonadotrophin-releasing hormone (GnRH) • the anterior lobe of pituitary – growth hormone (GH) – follicle-stimulating hormone (FSH) – luteinizing hormone (LH) – thyroid-stimulating hormone (TSH) – adrenocorticotropic hormone (ACTH) • the posterior lobe of pituitary – oxytocin hormone – antidiuretic hormone (ADH) • thyroid – thyroxine hormone • pancreas – insulin hormone – glucagon hormone • adrenal – adrenaline hormone – aldosterone hormone • ovary – oestrogen hormone – progesterone hormone • testis – testosterone hormone 12.6.4 Discuss involvement of the nervous system and endocrine system in a “fight or flight” situation. 12.6.5 Compare and contrast the nervous and the endocrine system. 12.7 Health Issues Related to the Endocrine System 12.7.1 Predict the effects of hormonal imbalances on human health.

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12.1

Coordination and Response Organisms have the ability to detect changes in their environments and respond to these changes. This ability is called sensitivity while the change that stimulates the response is known as a stimulus (plural: stimuli). The stimulus is divided into two types, that is, external stimulus and internal stimulus. (a) Stimuli from the external environment include light, sound smell, taste, surrounding temperature, pressure and touch. (b) Stimuli from the internal environment include changes in blood osmotic pressure, changes in body temperature and changes in blood sugar level. Mammals can detect stimuli via the special sensory cells known as receptors. When a receptor detects a stimulus such as sound, the stimulus is converted to nerve impulses. Nerve impulses are sent to the brain through nerve cells or neurones. The brain is the integration centre that translates nerve impulses and coordinates an appropriate response. Response refers to the way organisms react after detecting a stimulus. The part of the body that responds is called the effector. Examples of effectors are muscles and glands. Figure 12.1 and Figure 12.2 explain the main components and pathways involved in detecting and responding to changes in external and internal environments.

In the integration centre (the brain), nerve impulses are interpreted and a response is triggered

Stimulus from the external environment (example: the sound of phone ringing)

Im mo pul tor ses ne ar ur e s on en et tt o t hro he ug eff h t ec he tor

Detected by sensory receptors in the sensory organs and transformed into nerve impulses

nt ne se euro e r n s a ry re lu se nso cent e p im he s tion e t v r h gra Ne roug inte th the to

Effector (hand muscles) produces a response (answering the telephone) FIGURE 12.1 Main components and pathways involved in detecting and responding to changes in the external environment

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12.1.1

12.1.2

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Receptors and effectors work together to bring suitable changes depending on the stimulus detected. Coordination is a stimuli detection process by receptors that ends in appropriate responses by effectors. Coordination ensures that the overall activities and systems of an organism function and are synchronised perfectly as a complete unit. The role of coordination and response is conducted by two separate systems, that is, the nervous system and the endocrine system. Both systems work together to coordinate and control responses.

Detected by receptors (baroreceptor) in the aortic arch and carotid artery

Nerve impulses are sent through the sensory neurone to the integration centre

Activity Zone Conduct a role play activity to explain coordination and responses.

Integration centre (cardiovascular control centre in the medulla oblongata) The cardiovascular control centre sends nerve impulses through the motor neurone to the effectors

CHAPTER 12

Stimulus from the internal environment (example: blood pressure increases during running)

The effectors react (weakened contraction of cardiac muscles and the expansion of blood vessels’ diameter) to reduce the blood pressure to the normal range

FIGURE 12.2 The main components and pathways involved in detecting and responding to changes in the internal environment 12.1.1

12.1.2

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Types of receptors Sensory receptors found at the end of the nerve fibres detect information in the external and internal environments. The location of receptors will depend on the type of stimulus detected. Each type of receptor is usually sensitive to a specific stimulus. For example, the sensory receptors that detect external stimuli are found in special sensory organs such as eyes, nose, tongue and skin. The sensory receptors that detect internal stimuli are present in specific internal organs such as the pancreatic cells that detect blood sugar level.

Across the fields All receptors can be considered as energy converters, that is, receptors can convert one form of energy into another. For example, the eye photoreceptor converts light energy into electrical signals, which is a form accepted by the nervous system.

TABLE 12.1 Types of sensory receptors and stimulus involved

Sensory receptor

Stimulus

Photoreceptor

Light

Thermoreceptor

Change in temperature

Chemoreceptor

Chemical substances

Baroreceptor

Change in pressure

Mechanoreceptor

Touch and pressure

Nociceptor

Pain

receptor (photoreceptor)

integration centre (the brain)

light stimulus

sensory neurone (optic nerve)

FIGURE 12.3 Detection of external stimulus by the photoreceptor

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12.1.3

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PHOTOGRAPH 12.1 Animals migrate when they sense changes in the climate

Necessity of response

Formative Practice

12.1

1 What is the meaning of response? 2 Which sensory organ has the mechanoreceptor as a sensory receptor? 3 In your opinion, why is coordination crucial to humans?

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PHOTOGRAPH 12.2 A fast response is necessary to save a goal

CHAPTER 12

Why do organisms have to respond to stimuli and internal stimuli? The ability of organisms to detect changes in the external environment and its response to the stimuli is very important for the survival of organisms. For some animals, a sudden change in climate conditions motivates the animals to look for new shelters. The ability of organisms to detect changes in the internal environment is also crucial so that the information can be transmitted to the integration centre. The integration centre will then transmit this information to the effectors to respond to the changes. For example, when the body temperature increases above the normal range, this information will be transmitted to the integration centre by a receptor. The integration centre will send nerve impulses to the effectors to decrease the temperature back to its normal range. In conclusion, humans and animals need to respond to adapt to the changes in the environment.

4 You feel a mosquito bite on your leg and you hit it. Desribe the pathway involved in detecting and responding to the stimulus of the mosquito bite.

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12.2 brain CENTRAL NERVOUS SYSTEM

Nervous System The human nervous system is made up of a network of nerve cells or neurones. This system is divided into two main subsystems: the central nervous system and the peripheral nervous system (Figure 12.4). The central nervous system includes the brain and spinal cord. The peripheral nervous system consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves. The cranial nerves send nerve impulses from and to the brain. Spinal nerves send nerve impulses from and to the spinal cord. cranial nerve

spinal cord spinal nerve

PERIPHERAL NERVOUS SYSTEM

sensory receptor

FIGURE 12.4 A schematic diagram showing the organisation of the human nervous system

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Brain Do you know that the brain is made up of more than 100 billion neurones? The brain is the coordination and control centre for humans. The main components of the brain are the cerebrum, hypothalamus, cerebellum, medulla oblongata and pituitary gland (Figure 12.5).

AR

CEREBRUM

• The largest and most complex structure present in the frontal part of the brain. • The surface is folded to increase the surface area to hold more nerves. • It is the centre that controls emotions, hearing, sight, personality and controlled actions. • The cerebrum receives information and stimulus from the receptor. • This information is analysed, integrated and correlated to produce sensory perception. • The response is determined and instructions are given to the effectors. • The cerebrum is also responsible for higher mental abilities such as learning, memorising, linguistic skills and mathematics skills.

CEREBELLUM

HYPOTHALAMUS

• It is the control centre that regulates body temperature, water balance, blood pressure, and senses hunger, thirst and fatigue. • The hypothalamus connects the nervous system to the endocrine system through the pituitary gland. • Controls the secretion of a few types of pituitary gland hormones.

Maintains body balance and coordination of muscle contraction for body movement.

spinal cord CHAPTER 12

• Coordinating homeostasis.

FIGURE 12.5 Human brain

PITUITARY GLAND

• Located at the base of the hypothalamus. • The main gland in the endocrine system. • This gland secretes hormones that control the secretion of hormones by other endocrine glands. 12.2.2

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MEDULLA OBLONGATA

• Located at the anterior of the cerebellum. • Controls involuntary actions such as heartbeat, breathing, food digestion, vasoconstriction, blood pressure, peristalsis, vomiting, coughing, sneezing and swallowing.

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Spinal cord

Brainstorm! In a newly operated section of the spinal cord, the white matter appears white and the grey matter appears grey. Can you explain why?

The spinal cord is contained within the vertebral column and is surrounded by cerebrospinal fluid that protects and supplies the spinal cord with nutrients. The spinal cord is made up of white matter and grey matter (Figure 12.6). In a cross section, the grey matter looks like a butterfly or the letter ‘H’. Grey matter comprises mainly of cell bodies and is surrounded by white matter. White matter consists of axons covered in myelin sheath and extends up and down the spinal cord. The spinal nerve extends from the spinal cord through two short branches or roots which are the dorsal root and ventral root. The function of the spinal cord is to (a) process a few types of sensory information and to send responses through the motor neurones (b) control reflex action (c) connect the brain with the peripheral nervous system The detailed functions of the spinal cord structure is summarised in Figure 12.6. DORSAL ROOT

DORSAL ROOT GANGLION

The dorsal root contains the axon of the sensory neurone that sends nerve impulses from the sensory receptor to the spinal cord.

The sensory neurones’ cell bodies are clustered in the dorsal root ganglion

relay neurone

sensory neurone

grey matter

white matter (contains myelin-coated axon) VENTRAL ROOT

The ventral root contains the motor neurone that sends nerve impulses from the spinal cord to the effector.

SPINAL NERVE motor neurone

The spinal nerve contains the sensory neurone and motor neurone.

FIGURE 12.6 Cross section showing the detailed structure of the spinal cord, white matter and grey matter

Peripheral nervous system The peripheral nervous system consists of the somatic nervous system and autonomic nervous system. The somatic nervous system regulates all controlled actions. The autonomic nervous system controls involuntary actions such as heartbeat and contraction of the blood vessel. The function of the peripheral nervous system is to connect sensory receptors and effectors to the central nervous system. 222

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12.2

1 Explain the role of the brain in body coordination. 2 Compare the functions of the cerebellum and the medulla oblongata.

12.3

Brainstorm! 3 State one difference between the functions of the somatic nervous system and the autonomic nervous system. 4 Explain why we cannot resist sneezing.

Neurones and Synapse The nervous system is made up of millions of nerve cells known as neurones. The basic structure of a neurone consists of a cell body, axon, dendrite, myelin sheath, a node of Ranvier and a synaptic knob (Figure 12.7). There are three types of neurones which are sensory neurones, relay neurones and motor neurones (Figure 12.8). AXON

DENDRITE

Axon is an elongated branch of the body cell. Axon carries impulses out of the cell body to other neurones or effectors.

Dendrites are short branches of the cell body. Dendrite receives nerve impulses from other neurones or the external environment and sends them to the cell body.

CELL BODY

A cell body consists of a nucleus and many cytoplasmic projections called dendrites. The cell body integrates signals and coordinates metabolic activities. NODE OF RANVIER

Certain neurones have parts that are not insulated by the myelin sheath at regular gaps along the axon. This gap is known as a node of Ranvier. The node of Ranvier helps to accelerate the flow of nerve impulses by allowing the nerve impulses to jump from one node to the following node. 12.3.1

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A person suffering from a stroke is having difficulty in moving his left hand. Which part of the brain is damaged?

direction of impulse flow

muscle cells

MYELIN SHEATH

Myelin sheath is an insulating membrane that coats the axon. Function of the myelin sheath: •

protects neurones from injury



functions as an insulator for electrical impulses



provides nutrients to the axon

CHAPTER 12

Formative Practice

SYNAPTIC KNOB

FIGURE 12.7 The basic structures and functions of the the parts of the neurone

The synaptic knob is a swelling at the end of the axon branch. The synaptic knob sends signals to muscle cells, gland cells or other neurone dendrites.

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dendrite

MOTOR NEURONE

axon

nucleus

• Can be found in the ventral root of the spinal nerve.

synaptic knob

direction of impulse flow

cell body

Motor neurone

• Receives nerve impulses from the relay neurone of the central nervous system and sends nerve impulses to effectors such as muscles or glands to produce the appropriate response. • The cell body is present in the grey matter of the spinal cord.

SENSORY NEURONE • Present in the dorsal root of the spinal nerve. • Carries nerve impulses from the sensory organ receptors to the central nervous system. • The cell body is found in the dorsal root ganglion. • Dendrites receive nerve impulses from receptors and send them to the cell body. • The nerve impulses are transferred from the cell body through the axon to the next neurone.

dendrite

direction of impulse flow dendrite

cell body

synaptic knob nucleus Relay neurone

direction of impulse flow

cell body Sensory neurone

nucleus

axon

synaptic knob

RELAY NEURONE • Nerve fibres found in the central nervous system. • Connects the sensory neurone to the motor neurone. • The cell body can be found in clusters in the grey matter of the central nervous system. • Sends nerve impulses from the sensory neurone to the central nervous system and from the central nervous system to the motor neurone.

FIGURE 12.8 Types and functions of neurones

Structure and functions of synapses Information is sent along the neurone through electrical signals known as nerve impulses. Impulses are positively charged waves that flow along the axon to the synaptic knob. There is a narrow gap called synapse that separates the synaptic knob from neurone dendrites that receive the impulses. Electrical signals that carry information must be transferred across synapses for impulses to be transmitted to the following neurone. 224

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Synapses play an important role in allowing nerve impulses to travel in one direction. Therefore, synapses control the types of impulses that pass through them.

Transmission of impulse across a synapse Impulses are transmitted chemically across synapses. The chemical substances involved are neurotransmitters that are kept in synaptic vesicles that are found at the end of the synaptic knob. Two examples of neurotransmitters found in most synapses are acetylcholine and noradrenaline. Other examples are serotonin and dopamine. The process of transmitting impulses through synapses is slow as it occurs chemically. At first, the electrical signal will be changed to a chemical signal in the form of a neurotransmitter, then the chemical substance is converted again to an electrical signal on the membrane of the receiving neurone. The transmission of impulses across synapses is shown in Figure 12.9.

2

The cobra’s poison can cause paralysis by preventing the action of the neurotransmitter.

ICT 12.1 Video: Synapse (Accessed on 21 August 2019)

When electrical impulses reach the synaptic knob, synaptic vesicles are stimulated to release neurotransmitters into the synapse.

The neurotransmitters diffuse through the synapse and combine to a specific receptor protein which is a receptor on the dendrite of the receiving neurone.

synaptic knob mitochondrion synaptic vesicle

neurotransmitter

receiving neurone

synapse

3

The binding of the neurotransmitter and the receptor stimulates the initiation of the next impulse so that impulse can be transmitted through the neurone.

1 2

3

receptor protein

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1

Biological Lens

FIGURE 12.9 Transmission of impulses across synapses

Synaptic knobs contain numerous mitochondria to generate the energy required for the transmission of nerve impulses. 12.3.4

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Formative Practice Activity Zone Design a simulation model of the nerve coordination using an electric circuit.

12.4

12.3

1 What is the function of motor neurones? 2 Why do synaptic knobs contain a lot of mitochondria?

4 Predict what would happen to the transmission of impulses if the neurone does not have a myelin sheath.

3 How are electrical impulses transmitted through synapses?

Voluntary and Involuntary Actions Responses produced are either voluntary action or involuntary action. What are the pathways of information transmission involved in both actions? What are the differences between voluntary action and involuntary action? Table 12.2 shows the comparison between voluntary and involuntary actions. TABLE 12.2 Comparison between voluntary action and involuntary action

Voluntary action

Involuntary action Similarity

Both actions involve stimulation, impulse, neurone and an effector organ.

Differences

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Actions that we are conscious of and done on our own will

Actions that occur automatically and occurs without us being conscious

Involves the somatic nervous system

Involves the autonomous nervous system

Controlled by the cerebral cortex

Controlled by the medulla oblongata and hypothalamus

Involves the reaction of the skeletal muscles

Involves the reaction of the smooth muscle and glands

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VOLUNTARY ACTIONS INVOLVING SKELETAL MUSCLES



Voluntary actions such as walking, talking or brushing teeth are conscious actions.



For example, you can voluntarily raise your hand to answer a question.



The voluntary actions involving the skeletal muscles are controlled by the cerebral cortex.



Since the information reaches the cerebral cortex, that is, our level of consciousness, our perception of the surroundings can be produced.



The information pathway in voluntary action is demonstrated in Figure 12.10.

3 The cerebrum interprets

1 Stimulus occurs

when the teacher questions pupils.

5 The pupil raises his

hand to answer the question (response).

2 The pupil’s receptor

receives the stimulus and transmits the nerve impulse to the cerebrum through the sensory neurone.

sensory neurone

the nerve impulse to be sent to the effector.

4 The effector (skeletal

muscles) receives the information.

motor neurone

relay neurone

FIGURE 12.10 The pathway of information transmission in voluntary actions that involve skeletal muscles

CHAPTER 12

Involuntary actions involving skeletal muscles: reflex response Three-neurone reflex arc • • • • • •

Several situations require immediate and spontaneous action. If you accidentally prick your finger on a sharp pin, you will move your finger immediately without much thought. This is known as a reflex action. A reflex action is a fast response a stimulus without being controlled by the brain. The nerve pathway involved in a reflex action is called the reflex arc (Figure 12.11). The reflex action of moving the finger from the sharp pin involves three neurones and communication between the neurones in the peripheral nervous system and the spinal cord.

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dorsal root ganglion cell body of sensory neurone

dorsal root spinal cord

3 relay neurone central canal

1 pin ventral spinal root nerve motor neurone 4

grey matter white matter cell body of motor neurone 5 effector

2 sensory neurone Sensory receptor stimulated

1 When a finger is pricked by a sharp pin, the sensory receptor detects the stimulus and triggers a nerve impulse.

2 The nerve impulse is transmitted along the sensory neurone to the spinal cord.

3

4

In the spinal cord, the nerve impulse is transferred from the sensory neurone through the synapse to the relay neurone.

From the relay neurone, the nerve impulse is transferred to the motor neurone.

5 The motor neurone transfers the nerve impulse from the spinal cord to the effector (muscle tissue) so that the finger can be moved quickly.

FIGURE 12.11 The reflex arc that involves three neurones and a spinal cord

The importance of reflex actions • • •

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Reflex actions produce spontaneous responses without waiting for instructions from the brain. The additional time that is needed by the brain to analyse information before triggering a response can lead to serious injuries. Since reflex actions involve the spinal cord, the brain can focus on higher-level thinking.

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Two-neurone reflex arc Another reflex action is the knee jerk or patellar reflex (Figure 12.12). This reflex uses the nerve pathway that involves two neurones, that is, the sensory neurone and the motor neurone. The doctor sometimes tests the effectiveness of someone’s nerve system by tapping on the knee using a rubber hammer (Photograph 12.3).

21.

When the tendon below the kneecap is knocked, the quadriceps muscle stretches and stimulates the stretch receptors to trigger nerve impulses.

stretch receptor

2 sensory neurone

The sensory neurone transmits the nerve impulses to the motor neurone in the spinal cord.

dorsal root dorsal root ganglion

spinal cord PHOTOGRAPH 12.3 Doctor testing knee jerk reflex

1

tendon below the kneecap

quadriceps muscle

leg jerks forward

grey matter

3

biceps femoris muscle

4

41.

motor neurone

ventral root

The quadriceps muscle contracts causing the leg to jerk to the front.

31.

The motor neurone then transmits impulses from the spinal cord to the quadriceps muscle.

white matter

Our World of Biology Reflex actions such as coughing protects the lungs from foreign particles from the external environment. The pupil reflex protects the retina from damage.

Activity Zone

CHAPTER 12

1

Draw a reflex arc. FIGURE 12.12 The reflex arc in knee jerk involving two neurones

Formative Practice

12.4

1 State the sequence of impulse transmission in the knee jerk reflex arc. 2 One example of reflex action is pulling the hand away from a hot object. Define the reflex action and state its importance.

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3 Differentiate between voluntary and involuntary actions. 4 Someone who loses a leg due to a certain disease will still feel pain in the area where the limb was amputated. Explain why.

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12.5 Our World of Biology The risk of Alzheimer’s disease is higher among individuals who rarely challenge their minds to study and think critically.

EPILEPSY

The occurrence of abnormal activities in certain parts of the brain causing the nerve cells to produce unusual signals. A person suffering from epilepsy may become unconscious and experience muscle spasms.

BRAIN PARALYSIS (CEREBRAL PALSY)

Brain paralysis occurs because of brain damage before or after a baby is born. It could also possibly occur in children between the ages of 3–5 years old. This disease causes failure in muscles and the ability of motor neurones to function properly.

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Health Issues Related to the Human Nervous System Nervous system disease

We should be thankful for having a central nervous system that functions well. However, the central nervous system can become damaged and stop functioning efficiently. A few examples of health issues related to the nervous system are given below. MULTIPLE SCLEROSIS

A progressive disease as a result of an abnormality in the immune system that attacks the myelin sheath in the brain and spinal cord. The damaged myelin sheath prevents the transmission of impulses from and to the brain. ALZHEIMER’S DISEASE

This disease causes the loss of ability to reason and to take care of oneself. The patient is usually confused, forgetful and disoriented even in a familiar place. If the deterioration of the brain continues, the patient will lose the ability to read, write, eat, walk and talk.

PARKINSON’S DISEASE

It is the shrinkage of the nervous system that causes tremors in the limbs, jaw, foot and face. The patient will also have difficulty maintaining body posture and balance.

LOU GEHRIG/AMYOTROPHIC LATERAL SCLEROSIS (ALS)

This disease is caused by the deterioration and death of motor neurones that control the movement of muscles such as chewing, walking and talking. ATTENTION-DEFICIT HYPERACTIVITY DISORDER (ADHD)

A type of brain disease that causes someone to become hyperactive, unable to concentrate and gets easily bored. AUTISM

A type of disease related to the development of nerves in the brain. Autism causes an individual to experience problems communicating and interacting. 12.5.1

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tivitcATraditional methods of treatment for health Activity 1.2sei12.1 issues related to the nervous system

Research study

Materials Medical magazines, Internet

Procedure Conduct a research study on the use of traditional methods (acupuncture, reflexology and others) in the treatment of health issues related to the nervous system.

Discussion What are the traditional methods that can treat health issues related to the nervous system?

The effects of drug and alcohol abuse on human coordination and response There are many types of drugs used for medical purposes, for example, marijuana is used by doctors in small quantities to reduce nausea in cancer patients after undergoing chemotherapy treatment. However, drug abuse other than for medical purposes can cause serious side effects and would most likely be fatal. Among the effects of drug abuse on drug addicts are: • addiction • an addiction that causes withdrawal symptoms such as shivering, sweating and vomiting if the drug is not taken

CHAPTER 12

Table 12.3 shows the effects of drug and alcohol on human coordination and response.

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TABLE 12.3 Drugs and alcohol and their effects on the nervous system

Substance

Effects

Stimulant drugs (stimulants)

• Increases the activity of the central nervous system • Excessive use causes temporary euphoria which is followed by depression

Sedative drugs (depressants)

• Delays the transmission of nerve impulses • Calms the mind

Hallucinogenic drugs

• Causes the user to hallucinate • Relief from pain and anxiety

Narcotic drugs

• Delays the normal functions of the brain

Alcohol

• Disrupts coordination and thinking • Delays the transfer of nerve impulses

Formative Practice

12.5

1 State the symptoms of Alzheimer’s disease. 2 Explain how drugs affect the coordination of one's nerves.

4 Explain why a drunk individual is not allowed to drive a vehicle.

3 Why do doctors use drugs in the treatment of cancer patients who undergo chemotherapy?

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12.6

Endocrine System The coordination system of the body needs cooperation between the endocrine system and the nervous system. Both systems play an important role in maintaining homeostasis. Even though both systems have different functions, they interact and complement each other to regulate and coordinate all processes and activities in the body. What is the endocrine system?

Endocrine System of Humans

Millennial Career Millennial Career Endocrinology is a branch of medicine that is related to the diseases of the endocrine system and problems with hormone secretion.

The endocrine system is made up of glands that secrete chemical substances, that is hormones. The endocrine glands are ductless glands. So, the hormones are secreted directly into the blood flow. Even though the hormones are transported throughout the body in the blood, the hormones only influence and affect specific target cells. The hormones bind with specific molecule receptors on the membrane surface of target cells and produce specific responses. The endocrine system of humans is made up of many glands. The glands secrete different hormones involved in specific physiological processes. The functions of hormones can be divided into three main functions: reproduction, growth and homeostasis. Figure 12.13 shows the endocrine glands.

hypothalamus

CHAPTER 12

pituitary gland

thyroid gland

adrenal gland pancreas ovary testis

FIGURE 12.13 The endocrine glands in the endocrine system of humans 12.6.1

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The functions of hormones secreted by each endocrine glands The pituitary gland is the main gland of the endocrine system because it secretes hormones that control the secretion of other endocrine glands. The pituitary gland is located at the bottom of the hypothalamus in the brain. The pituitary gland is made up of two lobes, which are the anterior lobe and the posterior lobe. Each lobe secretes hormones that have certain functions (Table 12.4 and Table 12.5). TABLE 12.4 The functions of hormones that are secreted by the posterior lobe of the pituitary gland

Posterior Lobe of the Pituitary Gland Hormone

Target Tissues/ Organs

Antidiuretic Kidney tubule (ADH)

Oxytocin

Function Stimulates the reabsorption of water

• Uterine muscles

• Stimulates the contraction of uterine muscles during birth

• Mammary glands

• Stimulates the production of milk from the mammary gland

anterior lobe hypothalamus

posterior lobe

TABLE 12.5 The functions of hormones that are secreted by the anterior lobe of the pituitary gland

Anterior Lobe of the Pituitary Gland Target Tissues/ Hormone Function Organs • Ovary • Stimulates ovulation, development of corpus luteum, Luteinizing hormone and secretion of oestrogen and progesterone (LH) • Testis • Stimulates secretion of testosterone Growth hormone Soft tissue, bone Stimulates growth, protein synthesis and fat metabolism (GH) Adrenocorticotropic Adrenal cortex Stimulates the adrenal cortex to secrete hormones hormone (ACTH) Thyroid-stimulating Thyroid gland Stimulates thyroid to secrete thyroxine hormone (TSH) • Ovary • Stimulates the development of follicles in the ovary Follicle-stimulating hormone (FSH) • Testis • Stimulates spermatogenesis

The hormone that regulates the secretion of other hormones is known as the stimulating hormone. This includes thyroid-stimulating hormone (TSH) and adrenocorticotropic hormone (ACTH). For example, TSH stimulates the thyroid gland to secrete thyroxine. Hormones that act directly on target organs include growth hormone, oxytocin and antidiuretic hormone (ADH). For example, GH acts directly on the bone. The hypothalamus secretes gonadotrophin-releasing hormone (GnRH). GnRH stimulates the pituitary gland to secrete FSH and LH into the blood. 234

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MALE

FEMALE THYROID GLAND

ADRENAL GLAND

Hormone: Thyroxine

Hormone: Aldosterone

Target tissues/organs: All tissues

Target tissues/organs: Kidney

Function:

Function: Increases the reabsorption of salt in kidneys

• Increases the metabolism rate • Increases body temperature

Hormone: Adrenaline

• Regulates growth and development

Target tissues/organs: Muscle tissues, liver and heart Function: • Increases the level of sugar and fatty acids in the blood

Hormone: Insulin

• Increases the respiratory rate and heartbeat

Target tissues/organs: Liver, muscles and adipose tissues

• Increases the rate of metabolism and contracts blood vessels

Function: Reduces blood glucose level and promotes the conversion of excess glucose to glycogen

PANCREAS

Hormone: Glucagon Target tissues/organs: Liver, muscles and adipose tissues Function: • Increases the blood glucose level

TESTIS

Hormone: Testosterone

OVARY

Target tissues/organs: Gonad, skin, muscles and bones

Hormone: Oestrogen

Function: Stimulates the development of secondary sexual characteristics in the male and spermatogenesis

• Stimulates the development of secondary sexual characteristics in the female and maturity of the follicles

FIGURE 12.14 The functions of hormones secreted by other endocrine glands

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CHAPTER 12

• Promotes the conversion of glycogen to glucose

Target tissues/organs: Gonad, skin, muscles and bones Function:

• Repairs and stimulates the thickening of the uterus wall Hormone: Progesterone Target tissues/organs: Gonad Function: Stimulates the development of the uterus wall and the formation of the placenta

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Involvement of the nervous system and endocrine system in a ‘fight or flight’ situation Have you ever been in a state of ‘fight or flight’ situation? For example, when a dog or a goose suddenly chases you? How do you feel in a situation like this? Your heart will beat fast and your palms will sweat. What causes this condition?

In an emergency or a ‘fight or flight’ situation, the hypothalamus transmits nerve impulses directly to the adrenal medulla and the adrenal medulla cells are stimulated to secrete adrenaline and noradrenaline. These two hormones act quickly to produce the required responses in a ‘fight or flight’ situation. This includes an increase in: • heart rate • respiratory rate • blood pressure • blood glucose level • metabolic activity The heart pumps more oxygen and glucose to the brain and skeletal muscles because additional energy is needed to fight or run quickly. In an emergency, both the endocrine system and the nervous system work together to produce an immediate response to deal with the dangerous situation. When this mechanism manages to control this ‘fight or flight’ situation, bodily changes that have occurred return to the normal range. What are the similarities and differences between the endocrine system and the nervous system? Figure 12.15 compares and contrasts the two systems. 236

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It is made up of a network of millions of neurones

The duration of the effect is short

The duration of the effect is long

Consists of ductless endocrine glands

ENDOCRINE SYSTEM

Signal is delivered by organic chemical substances, which are hormones, through blood flow

Contains target tissues or organs

Signal is in the form of electrical impulses through neurones

Nerve response is quick and immediate

NERVOUS SYSTEM

Produces a response to a stimulus

Functions to regulate all activities of the body The effect of an impulse produces the response of an organ

The effect of hormones produces responses in several organs

The response is slow and prolonged

FIGURE 12.15 Similarities and differences between the nervous system and the endocrine system

The endocrine system plays a key role in maintaining the homeostasis of the body. However, an imbalance in hormone production can occur in some individuals when the endocrine gland secretes excessive or insufficient hormone. What is the effect of hormone imbalance to the individual?

12.6

1 Name the hormone that is related to the function given.

Hormone

Function Stimulates the contraction of uterine muscles during birth Stimulates water absorption by the kidneys

2 State three characteristics of hormones. 3 Compare between the nervous system and the endocrine system. 4 A pupil finds herself being followed by a van and suspects there is an attempt to kidnap her. In a state of panic, the pupil is able to run fast and far away from the van. Explain the ‘fight or flight’ in this situation.

CHAPTER 12

Formative Practice

Increases the metabolism rate of most of the body cells

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12.7

Health Issues Related to the Human Endocrine System

DIABETES MELLITUS

DIABETES INSIPIDUS For diabetes insipidus patients, the posterior lobe of the pituitary gland fails to secrete the antidiuretic hormone (ADH). As a result, patients will produce a large amount of urine and often feel thirsty. Since a large amount of water is lost through the urine, the individual will experience dehydration if they do not drink enough water every day.

A diabetes mellitus patient does not produce enough insulin or cannot use the insulin produced. As a result, the level of glucose in the blood is high. The patient urinates frequently, is always thirsty, experiences numbness in the soles of the feet, has blurred vision, is tired and their wounds heal much slower. Whereas, the excessive secretion of insulin causes hypoglycaemia where the blood glucose level is too low. Among the symptoms of hypoglycaemia are fatigue, difficulties sleeping at night, disordered thoughts, fear, emotional instability, faints easily and headache.

dry, rough and sparse hair

HYPOTHYROIDISM

thin eyebrows

An adult will experience hypothyroidism if there is inadequate thyroxine secretion. Symptoms include extremely slow heartbeat, extremely sensitive to cold, tiredness and gain weight easily.

oedema bloated, dry skin

PHOTOGRAPH 12.4 An individual who has hypothyroidism

HYPERTHYROIDISM Hyperthyroidism refers to a situation that occurs when too much thyroxine is secreted. Symptoms include excessive sweating, heat intolerance, increased frequency of defaecation, fear, heart palpitations and weight loss. Sometimes, the thyroid gland will grow two or three times larger than its original size (Photograph 12.5).

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PHOTOGRAPH 12.5 Enlarged thyroid gland 12.7.1

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hands of a child with gigantism

PHOTOGRAPH 12.6 The hands of a 12-year-old boy with gigantism. Observe that his hands are bigger than that of a normal adult

GIGANTISM

Excessive secretion of the growth hormone (GH) during childhood causes gigantism which is a condition characterised by the abnormal elongation of bones (Photograph 12.6). The individual grows to become extremely tall.

Formative Practice

PHOTOGRAPH 12.7 Chandra Bahadur Dangi from Nepal (0.55 m), the shortest man in the world and Sultan Kosen (2.47 m), the tallest man in the world DWARFISM

Low secretion of the growth hormone (GH) during the period of growth delays the growth of bones and causes a condition called dwarfism (Photograph 12.7). Organs also fail to develop and parts of the body ratio remain as that of a child.

CHAPTER 12

hands of a normal adult

12.7

1 State the factors that cause a person to contract diabetes insipidus. 2 State two symptoms experienced by people with diabetes mellitus.

3 Goitre is a disease that causes the enlargement of the thyroid gland. In your opinion, why are goitre patients encouraged to eat seafood? 4 Suggest a treatment for children with stunted growth due to growth hormone deficiency.

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Summary COORDINATION AND RESPONSE IN HUMANS

Coordination and Response • Stimulus • Receptor • Integration centre • Effector • Response

Nervous System Central nervous system Interpreting information and sending a response to an effector through the motor neurones • Brain • Spinal cord

Peripheral nervous system Linking the sensory receptor and effector with the central nervous system • Sensory receptor – Chemoreceptor: Detects chemical substances – Mechanoreceptor: Detects touch and pressure stimulation – Photoreceptor: Detects light – Thermoreceptor: Detects change in temperature – Baroreceptor: Detects change in pressure – Nociceptor: Detects pain • Somatic nervous system Controlling voluntary actions • Autonomous nervous system Controlling involuntary actions

Neurones and Synapse

Endocrine System • Endocrine gland • Hormone • Involvement of the nervous and endocrine system in a “fight or flight” situation • Compare and contrast the nervous and the endocrine system

• Sensory neurones • Relay neurones • Motor neurones Type of Action Voluntary action Actions that we are conscious of and done on our own will Involuntary action Action that occurs automatically and involves an autonomous nervous system and controlled by the medulla oblongata

Health Issues Related to the Human Endocrine System

Health Issues Related to the Human Nervous System • Multiple sclerosis • Alzheimer's disease • Parkinson's disease • Lou Gehrig/ Amyotrophic Lateral Sclerosis (ALS)

• Dwarfism • Gigantism • Hyperthyroidism • Hypothyroidism • Diabetes mellitus • Diabetes insipidus

• Attention Deficit Hyperactivity Disorder (ADHD) • Autism • Brain paralysis (Cerebral palsy) • Epilepsy

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Self Reflection Have you mastered the following important concepts? • Sequence of components in the coordination of humans • Structure of the human ner vous system • Functions of the brain • Function of a neurone in the transmission of impulse • Structure and functions of synapses • Transmission of a ner ve impulse across a synapse • Voluntary and involuntary actions • Reflex arc involving t wo neurones and three neurones • Health issues related to the ner vous system • Effects of drug and alcohol abuse on coordination • Functions of hormones secreted by endocrine glands • Compare and contrast the ner vous and the endocrine system • The effects of hormonal imbalance on human health

Summative Practice 12 1 Compare the functions of the cerebellum and the medulla oblongata. 2 Define reflex action and state its importance. 3 Name the main endocrine gland in the endocrine system of humans. Why is this gland considered the main gland? 4 State the effects of excessive and insufficient growth hormones (GH) in humans.

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5 Figure 1 shows the cross section of a part of the nervous system. (a) (i) Name structure X. X (ii) State the function of structure X. (b) Why is part Y swollen? (c) Complete Figure 1 with neurones involved in a reflex action. Mark the direction of impulse on the neurone. (d) If the spinal nerve is cut at Z, what is the effect on the organ that is connected to it? Explain why.

Y

Z

FIGURE 1

6 Figure 2(a) shows part of a motor neurone and Figure 2(b) shows a cross section of a synaptic knob. Impulse direction from nearby neurones V U T

axon S





(a)

(b) FIGURE 2

(a) Name the parts labelled V, T and U. (b) Name the chemical substances in U. (c) The synaptic knob contains a lot of V. What is the function of V? (d) Draw an arrow that shows the direction of impulse flow along axon S. (e) Explain (i) why does the transmission of impulse involve the pathway of impulse through T. (ii) how transmission of impulse occurs. (f) Based on Figures 2(a) and (b), explain why transmission of impulse through a neurone occurs in one direction only.

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Essay Questions 7 Explain the effects of stimulant drugs and sedative drugs on the transmission of impulse through the synapse. 8 (a) (i) Compare and contrast the nervous system and the endocrine system. (ii) Nora accidentally stepped on a nail. She screamed while holding on to her injured foot. Describe Nora’s reaction when she stepped on the nail. (b) After tea time, Azman went to the playground to ride his bicycle. While riding his bicycle, Azman is conscious of his action. However, he is not conscious of what is happening to the food that he had just eaten. Describe why Azman is conscious of his action riding the bicycle but is not conscious of the food he had just eaten. Enrichment 9 How does the brain decide in determining how much energy is needed to lift a piece of paper compared to a book? 10 Explain why we have to understand and display a lot of patience when taking care of an Alzheimer’s or Parkinson’s patient.

Complete answers are available by scanning the QR code provided

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13 CHAPTER

Homeostasis and the Human Urinary System

Do you KNOW…

How can diabetes cause kidney failure?

• What does hom eostasis mean? • How are your bo dy temperature, blood sugar level, th e partial pressure of carbon dioxide an d blood pressure regulated? • What is the struc ture and function of the kidney? • How is urine form ed? • How does the ne gative feedback mechanism in hom eostasis happen? • What are the he alth issues related to the urinary syste m?

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13.1 Homeostasis 13.1.1 Explain the meaning of homeostasis. 13.1.2 Justify the necessity to maintain physical and chemical factors in the internal environment. 13.1.3 Describe the involvement of various organ systems in maintaining an optimal internal environment. 13.1.4 Apply the knowledge of homeostasis concept in regulation of: • body temperature • blood sugar levels • the partial pressure of carbon dioxide • blood pressure

Glomeruli and renal tubules

13.2 Urinary System 13.2.1 Identify the structure and functions of a kidney. 13.2.2 Draw, label and explain the structure of a nephron and collecting duct. 13.2.3 Describe the formation of urine: • ultrafiltration • reabsorption • secretion 13.2.4 Synthesise the concept of homeostasis by using negative feedback mechanism in osmoregulation. 13.2.5 Conduct an experiment to study the effects of different volumes of water intake on urine formation. 13.3 Health Issues Related to the Urinary System 13.3.1 Describe health issues that are related to the urinary system.

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13.1

Homeostasis Homeostasis Homeostasis is the regulation of physical and chemical factors of the internal environment within normal ranges for the cell to function in optimum conditions.

Physical and chemical factors of the internal environment

Val ue

in

se s ea cr

The physical factors that need to be regulated are temperature, osmotic blood pressure and blood pressure. The Regulatory chemicals that need to be regulated are pH value, V alu system s ed se a the concentration of minerals and blood sugar e e cr concentrations. Any deviation from the normal range triggers the homeostatic mechanism which involves negative feedback. Homeostasis regulates the Homeostatic Normal Normal internal environment in order for it to be in a mechanism range range constant state although the external environment changes a lot. This ensures that cell activity continues to function at the optimum level. Figure 13.1 shows the negative feedback mechanism ec rea nc i of homeostasis. ses Regulatory ue Val In homeostasis, system (a) a factor that exceeds the normal range is brought down to the normal range FIGURE 13.1 Deviation from the normal range triggers (b)  a factor that falls below the normal range is the mechanism of homeostasis to return a factor’s value increased to the normal range to the normal range d

re as es

ue Val

The organ system involved in maintaining an optimal internal environment In the body, various organ systems function and interact with each other to maintain an optimum internal environment. • • • • 246

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Body temperature is regulated by the integumentary system (skin and sweat glands), nervous system, circulatory system, muscle system and endocrine system. Blood sugar levels are regulated by the endocrine gland, circulatory system and digestive system. The partial pressure of carbon dioxide in the blood is regulated by the respiratory system, circulatory system and nervous system. Blood pressure is regulated by the circulatory system and nervous system. 13.1.1

13.1.2

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Regulating body temperature Maintaining the body temperature at a fixed range is important so that cell metabolism reactions that are catalysed by enzymes occur at optimum levels. Temperatures that are too high will denature enzymes, while temperatures that are too low will slow down the metabolic activity of the cell, and prevent it from carrying out cell processes. These changes in body temperature are detected by the thermoreceptors in the skin and the hypothalamus. Figure 13.2 shows the regulation of body temperature by different effectors when the body temperature increases beyond normal ranges. Figure 13.3 shows the regulation of body temperature by different effectors when the body temperature decreases below normal ranges. Thermoreceptors in the hypothalamus Body temperature rises above normal ranges

detected by

hypothalamus (temperature control centre)

Thermoreceptors in the skin

pituitary gland

Regulation of Body Temperature by Effectors through Physical Methods heat loss through the epidermis

Skeletal muscles contract and relax less. The body does not shiver.

fine hair lowers towards the skin surface

erector muscles relax

skeletal muscles

Arterioles in the skin dilate (vasodilation) to allow more blood to flow to the skin surface. More heat is lost to the external environment through radiation.

epidermis (skin)

arteriole dilates

The sweat glands are stimulated to produce more sweat. Heat is absorbed to evaporate sweat, and this cools the skin. CHAPTER 13

Erector muscles are less stimulated so they do not constrict and the fine hair will lower towards the skin surface. As a result, a thin layer of air is trapped between the fine hair. Heat can be released quickly.

Regulation of Body Temperature by Effectors through Chemical Methods adrenal gland

The adrenal glands are less stimulated to secrete adrenaline. Metabolic rate decreases.

kidney

The thyroid gland is not stimulated and the secretion of thyroxine is reduced. Metabolic rate decreases. No excess heat is generated.

FIGURE 13.2 Body temperature regulation when temperature increases 13.1.4

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larynx

thyroid gland trachea

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Body temperature drops below normal ranges

Thermoreceptors in the hypothalamus hypothalamus (temperature control centre)

detected by

Thermoreceptors in the skin

pituitary gland

Regulation of Body Temperature by Effectors through Physical Methods epidermis (skin)

Erector muscles are stimulated so they contract, causing fine hair to stand erect. A thick layer of air trapped between the fine hairs acts as an insulator that prevents loss of heat from the skin.

fine hairs raised

erector muscles contract

Arterioles in the skin are stimulated to constrict (vasoconstriction). The result is less blood flow to the surface of the skin. With that, less heat is lost to the external environment through radiation.

arteriole constricts

liang

sweat peluh pore

skeletal muscles

Skeletal muscles will contract and relax so the body will shiver. This generates heat which in turn raises the body temperature because the constriction of muscles requires energy.

The sweat gland is not stimulated. Sweating does not happen.

kelenjar sweat peluh gland

Regulation of Body Temperature by Effectors through Chemical Methods

The adrenal glands are stimulated to secrete more adrenaline. This hormone speeds up the conversion of glycogen to glucose. Metabolic rate increases. The oxidation of glucose releases heat to warm the body.

adrenal gland

kidney

The thyroid gland is stimulated to secrete more thyroxine which will increase the metabolic rate. More heat is generated for the body.

larynx

thyroid gland trachea

FIGURE 13.3 Body temperature regulation when temperature decreases

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Regulation of blood sugar levels

Malaysian Innovation

The pancreas is responsible for maintaining blood sugar (glucose) levels within the normal range of 75–110 mg/100 ml. Langerhans cells in the pancreas produce and secrete insulin and glucose continuously into the bloodstream to regulate blood sugar levels. The actions of both these hormones and the mechanism of homeostasis work together to maintain the blood sugar levels within the normal range as described in Figure 13.4.

Scientific studies have confirmed that cinnamon can lower blood sugar levels.

Blood sugar levels drop (in between meals)

Blood sugar levels increase (after a meal) pancreas



Insulin stimulates the muscle cells to use glucose in the process of cell respiration.



Insulin stimulates the conversion of excess glucose into glycogen to be stored in the liver and muscle cells.



In adipose cells, insulin converts excess glucose to fat.

Alpha cells (α) in pancreatic Langerhans cells are stimulated to secrete glucagon into the blood.

liver



Glucagon stimulates liver cells to convert glycogen to glucose.



Glucagon also promotes the breakdown of fat to release fatty acids that can be metabolised to produce energy.

adipose cells negative feedback

Blood sugar levels go back to normal

CHAPTER 13

Beta (β) cells in pancreatic Langerhans cells are stimulated to secrete insulin into the blood.

FIGURE 13.4 Regulation of blood sugar levels

Failure in the production, secretion and intake of insulin by target cells can cause diabetes mellitus. The blood sugar level of diabetic patients is usually high and unstable after a meal. The patient also feels thirsty, tired, fatigued and suffers weight loss. Diabetes mellitus can be controlled through insulin injections, pills that lower blood sugar levels and a proper diet. 13.1.4

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ICT 13.1 Video: Regulating blood sugar levels in normal individuals and diabetic patients (Accessed August 21 2019)

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Our World of Biology Noni fruit (Morinda citrifolia) is believed to be able to lower high blood pressure. Juice extracted from this fruit has been marketed on a large scale.

Regulation of partial pressure of carbon dioxide in the blood Breathing is an involuntary action that is regulated by the respiratory control centre in the medulla oblongata. The respiratory control centre helps maintain homeostasis by controlling the partial pressure of carbon dioxide in the blood (Figure 13.5). During vigorous activity, the partial pressure of carbon dioxide increases because of cellular respiration.

Carbon dioxide dissolves in blood plasma to form carbonic acid. Carbonic acid is broken down into hydrogen ions and bicarbonate ions. Carbon + Water dioxide

Carbonic acid

Hydrogen Bicarbonate + ion ion

carotid body

pH values of blood and tissue fluid that flood the brain (cerebrospinal fluid) decreases.

baroreceptors in the carotid artery

carotid artery

Respiration control centre and cardiovascular control centre inside the medulla oblongata.

Nerve impulses triggered and sent

cerebrum

This change in pH is detected by the central chemoreceptor in the medulla oblongata (sensory cells that are sensitive to chemicals) and peripheral chemoreceptor in the neck (carotid body and aortic body) (Figure 13.6).

medulla oblongata nerve impulse sent

aortic body baroreceptor in the aortic arch

aortic arch

heart FIGURE 13.6 Aortic body, carotid body and baroreceptor

intercostal muscles

Intercostal muscles, diaphragm and cardiac muscles contract and relax quickly.

Breathing rate, heart rate and ventilation rate increase. This causes more carbon dioxide gas to be expelled from the lungs.

Partial pressure of carbon dioxide and blood pH levels go back to normal. diaphragm

FIGURE 13.5 Process of regulating partial pressure of carbon dioxide in the blood

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13.1.4

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Blood pressure regulation mechanism Baroreceptors or pressure receptors are located in the aortic arch and carotid artery (Figure 13.6). The carotid artery is the artery in the neck that supplies blood to the head. These receptors detect the pressure of blood flowing through them and continuously send impulses to the cardiovascular control centre in the medulla oblongata to regulate blood pressure (Figure 13.7).

When an individual’s blood pressure drops, for example, if there is serious bleeding.

When an individual’s blood pressure increases, for example during vigorous activities.

Baroreceptors in the aortic arch and carotid artery are stimulated.

Baroreceptors in the aortic arch and carotid artery are less stimulated.

The cardiovascular control centre in the medulla oblongata is less stimulated.

Vasoconstriction



Arterial vasoconstriction occurs. This adds resistance to the flow of blood in the bloodstream.



Stronger contractions of cardiac muscles occur.

The cardiovascular control centre in the medulla oblongata is stimulated.



Vasodilation occurs. This reduces the resistance of the flow of blood in the bloodstream.



Weak contractions of cardiac muscles occur.

Blood pressure returns to the normal ranges.

CHAPTER 13

blood pressure drops

blood pressure increases

Blood pressure returns to the normal ranges.

Vasodilation

FIGURE 13.7 Blood pressure regulation 13.1.4

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Formative Practice

13.1

1 What is the meaning of homeostasis? Explain how homeostasis happens. 2 An employee had to work in hot conditions because the power supply in his office got cut off. Describe the response of the effectors in regulating his body temperature. 3 A 40-year-old man was diagnosed by a doctor as unable to produce enough insulin. Describe what has happened to the man. 4 Ahmad has just finished a 100 m sprint run. Explain how his blood pressure is lowered back to normal range.

13.2

Urinary System The human urinary system plays an important role in homeostasis. The urinary system is made up of the kidneys, ureters, bladder and urethra (Figure 13.8). The function of the urinary system is to excrete nitrogenous compound wastes such as urea, as well as regulate the volume of body fluids, blood osmotic pressure, ion concentration in body fluids, electrolyte content and blood pH.

Structure and function of the kidneys Biological Lens Do you know that the right kidney is located lower than the left kidney? This difference in position is because the liver takes up a lot of space above the right kidney.

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The kidneys consist of the cortex and medulla. Urine that is formed in the kidneys flows into the pelvis. The kidneys have two main functions: (a) excretion (b) osmoregulation As an excretory organ, the kidneys excrete toxic wastes (nitrogenous compounds) such as urea, uric acid, ammonia and creatinine. As an osmoregulatory organ, the kidneys control: • the total volume of water in body fluids • the concentration of ions in body fluids • blood osmotic pressure, which is the concentration of dissolved materials and volume of blood and body fluids • electrolyte content and pH of blood and body fluids

13.2.1

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kidney renal artery renal vein

ureter

bladder

urethra

The renal artery carries oxygenated blood from the heart to the kidneys.

The renal vein carries deoxygenated blood from the kidneys back to the heart.

Urine flows to the bladder through the ureter.

CHAPTER 13

pelvis

medulla

cortex

FIGURE 13.8 Urinary system and cross section of the kidney 13.2.1

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Formation of urine There are three major processes involved in the production of urine, which are ultrafiltration, reabsorption and secretion. NEPHRON •

Each kidney is made up of millions of functional units called nephrons (Figure 13.9).



Each nephron is made up of the following structures: • Bowman’s capsule     • Glomerulus     • Renal tubule



Bowman’s capsule is cup-shaped and contains a cluster of blood capillaries called glomerulus. The glomerulus is formed from the afferent arteriole branching from the renal artery. The glomerulus merge again to form the efferent arteriole.



The renal tubules are composed of the proximal convoluted tubules, loop of Henle and distal convoluted tubule.



The loop of Henle is a long U-shaped tubule that extends to the renal medulla. The distal convoluted tubule of several nephrons join together into a collecting duct.



The produced urine will flow from the collecting duct into the ureter. Indicator: blood flow flow of filtrate passive transport

blood flow afferent arteriole glomerulus

renal vein

Petunjuk:

Cl–

cortex

Na+ 2

filtrate from glomerulus

aliran d aliran h pengan pengan osmosis NaCl H2O

distal convoluted tubule

1

renal artery

glucose, amino acids urea

active transport osmosis

efferent arteriole

Bowman’s capsule

H2O

Cl– renal fluid

Na+

4 processed filtrate from other nephrons

proximal convoluted tubule + K+ H

medulla

5

glukosa urea

collecting duct urine to ureter

loop of Henle

3 blood capillary network

Na+ Cl–

FIGURE 13.9 Structure of the nephron and urine formation

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13.2.2

13.2.3

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1

ULTRAFILTRATION IN BOWMAN’S CAPSULE



Blood entering the glomerulus is under high hydrostatic pressure because the diameter of the afferent arteriole is larger than the diameter of the efferent arteriole. This pressure causes ultrafiltration to occur, that is, fluid seeps through the walls of the glomerulus capillaries into the cavity of Bowman’s capsule.



The fluid that enters Bowman’s capsule is known as the glomerular filtrate.



The glomerular filtrate has the same composition as blood plasma but does not contain red blood cells, platelets and plasma proteins.



Red blood cells and plasma proteins remain in the blood flowing to the efferent arteriole because the size of these substances is too large to seep out of the glomerulus.

2



REABSORPTION AT THE PROXIMAL CONVOLUTED TUBULES



Reabsorption of the glomerular filtrate occurs along the renal tubule. The dissolved substances permeate across the renal tubular walls into the blood capillary network.



In the proximal convoluted tubule, sodium ions (Na+) are actively pumped into the blood capillary network and chloride ions (Cl–) are passively absorbed.



The reabsorption of 100% glucose and amino acids also occurs through active transport.



The movement of dissolved substances into the blood capillary network reduces the concentration of dissolved substances in the glomerular filtrate but increases the concentration of dissolved substances in the blood capillaries. As a result, water enters the blood capillaries through osmosis.

REABSORPTION AT THE LOOP OF HENLE AND DISTAL CONVOLUTED TUBULES



In the loop of Henle, water is reabsorbed through osmosis. Sodium ions are reabsorbed through active transport.



In distal convoluted tubules, more water, sodium and chloride ions are reabsorbed.



The amount of water and salts reabsorbed depends on the water and salt content in the blood.

4

SECRETION



Secretion is the process of secreting waste materials in the blood that were not filtered earlier into the renal tubules.



This process is opposite to the process of reabsorption.



Secretion occurs along the renal tubule and collecting duct, but is most active at the distal convoluted tubule.



Secretion occurs through simple diffusion and active transport.



Substances that are secreted include hydrogen ions (H+), potassium ions (K+), ammonium ions (NH4+), urea, creatinine, toxic substances and some drugs.



Secretion gets rid of toxic wastes and helps to regulate the levels of ions in the blood.

13.2.2

13.2.3

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5

URINE FORMATION



When the renal fluid reaches the collecting duct, only a small amount of salts are left, and most of the water has been absorbed back into the bloodstream.



The remaining renal fluid is now called urine, flows down the collecting duct. Here, a small amount of urea diffuses out into the surrounding fluid and blood capillaries due to its small molecular size.



Urine contains water, urea, NaCl salt, uric acid and creatinine.



After leaving the collecting duct, urine flows through the ureter, bladder, urethra and is finally excreted.

CHAPTER 13

3

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Mechanism of homeostasis and osmoregulation The body’s water content constantly changes depending on the intake of food and drinks. Osmoregulation is the process of regulating water and salts in the body so that the blood osmotic pressure can be maintained at a normal range. Osmoregulation is achieved by regulating the volume of urine produced by the kidney. Figure 13.10 illustrates the osmoregulation of blood osmotic pressure. NORMAL BLOOD OSMOTIC PRESSURE

Drinking too little water or loss of water due to vigorous activity.

Drinking too much water.

1 Blood osmotic pressure increases above

1 Blood osmotic pressure drops to below

the normal range.

normal range.

2 Osmoreceptors in the hypothalamus are

2 Osmoreceptors in the hypothalamus are

stimulated.

less stimulated.

3 The pituitary gland is stimulated. So, more

3 The pituitary gland is less stimulated.

ADH is secreted from the pituitary gland.

So, less ADH is secreted from the pituitary gland.

4 High ADH concentrations cause the 4 Low ADH concentrations cause the walls of

the distal convoluted tubule and collecting duct to become less permeable to water. 5 Less water is reabsorbed from the renal fluid

into the blood capillary.

5 More water is absorbed from the renal fluid

into the blood capillary.

6 Less concentrated urine is generated in high

volumes.

walls of the distal convoluted tubule and the collecting duct to become more permeable to water.

6 Urine that is very concentrated and low in

volume is generated.

7 Blood osmotic pressure

returns to normal.

FIGURE 13.10 Osmoregulation of blood osmotic pressure

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13.2.4

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Carry out the following activity to better understand how consuming different volumes of water can affect urine production.

ivitkA Activity 1.2 it13.1

To study the effects of consuming different volumes of water on urine production

Experiment

Problem statement What is the effect of consuming different volumes of water on the volume of urine produced?

Hypothesis The higher the volume of water consumed, the higher the volume of urine produced.

Variables: Manipulated: Volume of water consumed Responding: Volume of urine collected Constant: Type of drink, age of pupil and time interval of urine collection

Specimen

Take Note!

Form 4 pupils

When identifying pupils for this study, choose pupils who are of approximately the same weight.

Materials Boiled water that has been cooled

Apparatus Cup, beaker to collect urine, stopwatch and measuring cylinder

Procedure 1 Pupils should not eat or drink after 12 midnight the night before the experiment. 2 Pupils are divided into four groups according to their average weight. 3 Pupils are required to urinate before starting the experiment. 4 Each pupil is required to drink the following volumes of water: (a) Group 1: drink 250 ml of water

(b) Group 2: drink 500 ml of water

(c) Group 3: drink 750 ml of water

(d) Group 4: drink 1000 ml of water

5 During the experiment, pupils should be at rest and are not allowed to carry out vigorous activities. 6 Collect and measure the urine for each pupil after 20 minutes, 40 minutes and 60 minutes. 7 As soon as the urine is measured, it must be discarded into the toilet. 8 Record the average volume of urine collected for each group, for each time interval in the following table. CHAPTER 13

9 Calculate the total volume of urine produced per group.

Results Group

Volume of water consumed (ml)

Average volume of urine collected (ml)

Total volume of urine produced (ml)

20 minutes 40 minutes 60 minutes 1

250

2 3 4

500 750 1000

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Discussion 1 What is the relationship between the volume of water consumed and the production of urine? Explain your answer. 2 How does the volume of urine change over time? 3 Explain how the volume of urine collected varies between an individual who drank 100 ml of distilled water, and an individual who drank 100 ml of 5% sodium chloride solution.

Conclusion Is the hypothesis accepted? State a suitable conclusion.

ivitkA Activity 1.2 it13.2

Gather information on and discuss haemodialysis

Collecting information

Materials Internet, reference materials

Procedure 1 In groups of four, gather information about haemodialysis. 2 Discuss the following. (a) Study the reasons of renal failure that cause a person to undergo haemodialysis. (b) Explain how haemodialysis works. 3 Make a report on your findings and present it to the class. 4 You can also carry out an activity to raise funds for haemodialysis centres through awareness campaigns about the importance of helping patients in need of treatment.

Discussion 1 Why would someone need haemodialysis? 2 How does haemodialysis work? 3 What is the effect on patients who do not receive treatment?

Formative Practice

13.2

1 In which part of the kidney can the proximal convoluted tubule, loop of Henle and distal convoluted tubule be found? 2 Suggest two possible activities that can cause the walls of the collecting duct to become more permeable to water.

4 An individual suffers damage in one kidney. Does the individual need to undergo haemodialysis? Suggest steps that this individual needs to take in order to go through his daily life without problems.

3 State how Na+ ions, water and glucose are reabsorbed into the proximal convoluted tubule.

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13.3

Health Issues Related to the Urinary System Kidney failure can be caused by illness, bacterial infections or accidents. Diabetes mellitus is the leading cause of renal failure, followed by high blood pressure. Both these conditions damage the glomerulus. Other than that, some individuals may face the problem of kidney stone formation. Kidney stones are hard masses made of uric acid, calcium oxalate or crystalline calcium phosphate.

ICT 13.2 Activity: Gather information and discuss health issues related to the urinary system

Kidney stones can block the ureter and reduce the production of urine. To reduce the likelihood of kidney stone formation, you should drink a lot of water every day. Why?

CHAPTER 13

kidney stone

FIGURE 13.11 Formation of kidney stones in the kidney

Formative Practice

13.3

1 Azman suffers from the formation of kidney stones. Explain the effects of kidney stones on his health. 13.3.1

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2 Suggest two reasons why a person would have kidney stones.

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Summary HOMEOSTASIS AND THE HUMAN URINARY SYSTEM

Homeostasis

Regulation of physical and chemical factors of the internal environment within normal ranges so that the cell functions at optimum levels

Body temperature Regulated by the integumentary system, nervous system, circulatory system, muscular system and endocrine system

Blood sugar level Regulated by the endocrine system, circulatory system and digestive system

The partial pressure of carbon dioxide in the blood Regulated by the respiration system, circulatory system and nervous system

Urinary System

Kidney: • Helps regulate water and salts in the body • The nephron is composed of the Bowman’s capsule, glomerulus, proximal convoluted tubule, loop of Henle and distal convoluted tubule

Health Issues Related to the Urinary System

Kidney stones

The process of urine formation • Ultrafiltration • Reabsorption • Secretion

Mechanism of homeostasis and osmoregulation • Osmoregulation of blood osmotic pressure

Blood pressure Regulated by the circulatory system and nervous system

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Self Reflection Have you mastered the following important concepts? • The meaning of homeostasis • The need to maintain the physical and chemical factors within the internal environment • The involvement of various organ systems in maintaining an optimum internal environment • The concept of homeostasis in regulation • Structure and function of the kidneys • Structure of the nephron and collecting duct • The process of urine formation • The concept of homeostasis and negative feedback in osmoregulation • Health issues related to the urinary system

Summative Practice 13 1 In which part of the kidney can the loop of Henle be found? 2 State the condition of urine that will be produced after an individual (a) drinks plenty of water (b) eats too much salty food

CHAPTER 13

3 State a test that you can perform in the laboratory to determine whether a person has diabetes. 4 Explain the role of the liver when blood sugar levels decrease. 5 Table 1 shows the concentration of amino acids in blood plasma and urine. TABLE 1





Contents

Concentration in blood plasma that enters the kidneys (g per 1000 ml)

Concentration in urine (g per 1000 ml)

Amino acids

85

0

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(a) Explain the difference in the concentration of amino acids in blood plasma and urine. (b) Both kidneys of a patient have failed. This condition causes water imbalance and an accumulation of urea in the blood. State the effect of kidney failure on the regulation of water balance in the blood. 6 (a) A patient suffered a disease that required the pancreas to be removed. Explain the effect of removing the pancreas on the production of enzymes and hormones, and subsequently on digestion and blood glucose levels in the individual. (b) What advice can be given to the patient to help him deal with the health problems caused by the removal of his pancreas? 7 Figure 1 shows the structure of a nephron and collecting duct. J

FIGURE 1

(a) Name the process that happens in J. (b) Name two substances that are not filtered out through the glomerulus. (c) Explain how the process you named in (a) occurs. (d) Explain why the fluid flowing in the loop of Henle does not contain glucose even though glucose is present in Bowman’s capsule. (e) Mammals have different kidney structures depending on the presence of water in their habitats. The concentration of urine produced depends on the length of the loop of Henle. The longer the loop of Henle, the higher the salt concentration in the fluid surrounding the loop of Henle. Based on this information, what can you predict about the loop of Henle in animals living in a humid environment compared to animals living in a dry environment?

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Essay Questions 8 Describe how the body temperature of a worker who has been in a cold room for 6 hours is regulated. 9 Breathing is an involuntary process that is controlled by the respiratory control centre in the medulla oblongata. Explain what happens to a climber’s breathing rate when he is at the peak of a high mountain. 10 Explain the role of erector muscles, fine hair and sweat glands in maintaining the body temperature on hot days. 11 (a) (i) Explain the importance of maintaining the body temperature at 37 °C. (ii) Describe two physical ways in which the body reacts to regulate body temperature after a person bathes with cold water. (b) In your opinion, what is the effect on urine excretion if the food consumed contains large quantities of protein? (c) Explain how the pituitary gland regulates blood osmotic pressure when a person drinks too little water. Enrichment 12 Explain how saltwater fish can survive without experiencing dehydration.

13 Why is a urine test conducted to determine if a person has taken drugs?

CHAPTER 13

14 Modern technology has greatly helped patients with kidney problems. For example, haemodialysis machines have helped many patients with kidney failure to survive. Currently, research is underway to produce bioartificial kidneys. This device is believed to be able to carry out all the functions of a healthy kidney. In your opinion, what qualities should a bioartificial kidney have in order to function like a real kidney?

Complete answers are available by scanning the QR code provided

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14 CHAPTER

Support and Movement in Humans and Animals

How are the fibres of the silk spider web used to aid the support system?

Do you KNOW…

• What are the typ es and characteris tics of bones that form the human skeleton? • What are the typ es of joints found in the human skeletal system? • How do human arms and legs mov e? • How do fish, bir ds, worms and grasshoppers mov e? • What are the he alth issues related to the human musculos keletal system?

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14.1 Types of Skeletons 14.1.1 List the types of skeletons in humans and animals: • hydrostatic skeleton • exoskeleton • endoskeleton 14.1.2 Justify the necessity of skeletons in humans and animals. 14.2 Musculoskeletal System of Humans 14.2.1 Identify the bones that form the human skeletal system: • axial skeleton • appendicular skeleton 14.2.2 Characterise the types of vertebrae in the backbone: • cervical vertebrae (including the atlas and axial) • thoracic vertebrae • lumbar vertebrae • sacral vertebrae • caudal vertebrae 14.2.3 Compare and contrast the types of vertebrae. 14.2.4 State the types of joints in the human skeletal system: • immovable joints • slightly moveable joints • freely moveable joints 14.2.5 Draw, label and explain the human forearm hinge joint structure: • bones • cartilages • skeletal muscles • tendons • ligaments • synovial membrane • synovial fluid

14.4 H  ealth Issues Related to the Human Musculoskeletal System 14.4.1 Describe the health issues related to the human musculoskeletal system: • osteoporosis • osteomalacia • rickets • arthritis • scoliosis 14.4.2 Justify the practices to maintain a healthy musculoskeletal system.

14.3 M  echanism of Movement and Locomotion 14.3.1 Explain the movement mechanisms in: • human forearm • human leg (walking) 14.3.2 Describe briefly the locomotion mechanisms in animals

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14.1

Types of Skeletons The skeletal system provides support to humans and animals. There are three types of skeletons, namely, the exoskeleton, endoskeleton and hydrostatic skeleton. Types of skeletons

ICT 14.1 Activity: Carry out a brainstorming activity on the necessity of support and movement in humans and animals

Brainstorm! What are the advantages and disadvantages if humans have exoskeletons like insects?

Endoskeleton in humans

Exoskeleton

Endoskeleton

The necessity of skeletal systems in animals and humans Humans and animals need the skeletal system to enable them to move from one place to another in search of food, partners, or to escape from predators and threats. Most multicellular organisms need support because of their soft body tissues. The exoskeleton found in insects and crabs, support and protect body organs and enable these animals to move. Animals with soft tissues such as earthworms need a hydrostatic skeleton to maintain a rigid body shape. The endoskeleton functions to maintain body shape, support soft body tissues and protect internal organs from injury. You will learn more about the human skeletal system in the following unit.

Formative Practice

14.1

1 Why do organisms need to maintain their body shapes? 2 State two functions of the skeletal system to humans.

Hydrostatic skeleton in earthworms

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Hydrostatic skeleton

3 For animals that move on the ground, what is the advantage of having legs below the body (for example, rats) compared to having legs at the side of the body (for example, crocodile)?

Exoskeleton in grasshoppers

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14.2

Musculoskeletal System of Humans Skeletal system The human skeletal system is made up of the axial skeleton and appendicular skeleton.

Axial skeleton The axial skeleton comprises the skull, vertebral column, ribs and sternum (breastbone).

Appendicular skeleton The appendicular skeleton includes the pectoral girdle, pelvic girdle, upper and lower limbs. Indicator:

skull

pectoral girdle

Axial skeleton Appendicular skeleton

clavicle sternum

scapula

rib cage ribs

humerus

vertebral column ulna upper limb

ilium

radius

pelvic girdle

carpus

pubis ischium

metacarpals

phalanges

femur

tibia

CHAPTER 14

patella lower limb

fibula

FIGURE 14.1 Human skeletal system 14.2.1

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tarsals metatarsals phalanges

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Human vertebral column

Activity Zone Carry out a brainstorming activity to explain the importance of skeleton to humans and animals.

The vertebrae (singular: vertebra) on different parts of the vertebral column differ in size and shape (Figures 14.2–14.7). Each vertebra has an opening known as the neural canal. The spinal cord is located in the neural canal. spinous process

cervical vertebrae

transverse process

neural canal

facet (articulation with the ribs)

facet (articulation with the vertebra above it) centrum

FIGURE 14.2 Thoracic vertebrae

Thoracic vertebrae (Figure 14.2) •

Possess a long spinous process



Spinous and transverse processes serve as attachment sites for muscles and ligaments



The transverse processes (except on the 11th and 12th thoracic vertebrae) have facets for articulation with the ribs.

Lumbar vertebrae (Figure 14.3) •

The biggest and strongest vertebrae



Possess a short spinous process



Possess a large centrum to bear the weight of the lower back of the body

spinous process

neural canal

thoracic vertebrae

facet

transverse process

centrum lumbar vertebrae FIGURE 14.3 Lumbar vertebrae

Sacral vertebrae (Figure 14.4)

process for articulation with the last lumbar vertebra

Five vertebrae fused together to form a triangular bone

passage for the nerves and blood vessels

Caudal vertebrae (Figure 14.4) caudal

FIGURE 14.4 Sacral and caudal vertebrae

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Four bones fused together to form a triangular structure which is pointed at one end.

sacrum

caudal 14.2.2

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spinous process

transverse process

neural canal facet

Atlas vertebra (Figure 14.5) •

The first cervical vertebra.



The vertebra has a large neural canal, a small spinous process, a pair of transverse foramina (singular: foramen) but with no centrum.



The vertebra articulates with the skull.

atlas vertebra

axial vertebra cervical vertebra

transverse foramen

FIGURE 14.5 Atlas vertebra

spinous process neural arch

Axial vertebra (Figure 14.6)

neural canal



The second cervical vertebra.



The axial vertebrae has a large spinous process, small transverse process and a pair of transverse foramina.



It has an odontoid process that articulates with the facet of the atlas vertebra’s neural canal. spinous process neural canal

facet

transverse process

odontoid process

transverse foramen

FIGURE 14.6 Axial vertebra

facet

Cervical vertebrae (Figure 14.7)

transverse foramen transverse process

centrum

Possess short spinous process, small centrum, wide and short transverse process, and a pair of transverse foramina.

FIGURE 14.7 Cervical vertebrae

Based on the characteristics shown, can you compare and contrast the different vertebrae? What are the differences between lumbar and thoracic vertebrae? What are the characteristics found on cervical vertebrae but not found on other vertebrae? SIMILARITY BETWEEN VERTEBRAE

All vertebrae have spinous and transverse processes, centrum (except the atlas vertebra) and neural canal.

CERVICAL VERTEBRAE

THORACIC VERTEBRAE

LUMBAR VERTEBRAE

• Short spinous process

• Long spinous process

• Short spinous process

• Wide and short transverse process

• Long transverse process

• Short transverse process

• Small centrum

• Medium-sized centrum

• Large centrum

• A pair of transverse foramina

• No transverse foramen

• No transverse foramen

14.2.2

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CHAPTER 14

DIFFERENCES BETWEEN VERTEBRAE

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How are these bones joined together to form the skeleton? Bones are too rigid to be bent without breaking. Flexible connective tissues form joints that hold the bones together so that movement can take place. We will learn about the different kinds of joints in the following section.

Joints Joints are points where two or more bones meet, or cartilage and bones meet. Most joints allow the bones to move relative to each other. Different types of joints allow different types of movements. The joints are divided into three types, namely, • immovable joints (for example, suture at the cranium of the skull) (Figure 14.8) • slightly moveable joints (for example, cartilage discs between the vertebrae, and cartilage between the first rib and sternum) (Figure 14.9) • freely moveable joints (for example, hinge joint and ball-and-socket joint) (Figure 14.10) clavicle

Activity Zone Dissect a chicken wing to observe the joint’s structure.

sternum

first rib cartilage suture

cartilage disc vertebra

suture FIGURE 14.8 Immovable joint

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FIGURE 14.9 Slightly moveable joints 14.2.4

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Freely moveable joints The ball-and-socket joint and hinge joint are two examples of freely moveable joints that allow free movements. The general structure of a freely moveable joint and the functions of its parts are shown in Figure 14.10. The capsule is the fibrous tissue that encloses and provides protection to the joint.

bone

Cartilage serves as a cushion to the joint, absorbs shocks and reduces friction between bone ends. The cartilage also protects the bones from wearing out.

The synovial membrane secretes synovial fluid into the synovial cavity.

The synovial fluid serves as a lubricant that reduces the friction between the ends of bones.

bone

PHOTOGRAPH 14.1 Joint

FIGURE 14.10 Freely moveable joint pelvic girdle

BALL-AND-SOCKET JOINT The ball-and-socket joint allows rotational movement in all directions (Figure 14.11). It allows the arm and leg to swing in a circular motion. Examples of ball-and-socket joints are the shoulder joints between the humerus and pectoral girdle, and the hip joint between the femur and pelvic girdle. FIGURE 14.11 Ball-and-socket joint at the hip

femur

HINGE JOINT

femur

fibula

CHAPTER 14

The hinge joint allows the movement of bones in one plane (Figure 14.12). For example, the knee joint allows the lower leg to swing back and forth, similar to a hinge on a door. The hinge joint can also be found at the elbow and phalanges of the fingers and toes. tibia FIGURE 14.12 Hinge joint at the knee

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Apart from joints and bones, support and movement also depend on the skeletal muscle, tendon and ligament.

skeletal muscle

humerus

tendon synovial membrane

radius

synovial fluid ulna

ligament

cartilage

FIGURE 14.13 Skeletal muscle, tendon and ligament

Electroactive plastic polymer is used to produce synthetic muscle. The plastic is used in the production of human-like robots and enables the robots to walk. The synthetic muscle contracts in response to electric current. It is also used to help those with missing limbs.

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• Comprises bundles of muscle fibres, with a large supply of nerves and blood vessels • The muscles work in pairs and act in opposite directions, that is if one muscle contracts, the other relaxes, and vice versa. These types of muscles are known as antagonistic muscles. • The biceps and triceps are examples of antagonistic muscles. The muscle that straightens the limbs when it contracts is called the extensor. For example, the triceps. The muscle that bends the limbs when it contracts is called the flexor. For example, biceps.

Tendon (connects bone and muscle) •

STEM Bulletin

Skeletal muscle

Consists of strong fibres, not elastic but flexible.

Ligament (connects bone to bone) •

Bones are held together at the joints by the ligament which consists of strong, elastic and tough connective tissue bundles.



The ligament provides support and strength to joints and allows bones to be bent at the joints.

Formative Practice

14.2

1 Name the bones that form the axial skeleton of the human body.

3 State the differences between the structure and function of tendon and ligament.

2 State the function of cartilage and synovial fluid in the joint.

4 Explain the differences between the ball-and-socket joint and hinge joint.

Movement and Locomotion The mechanism for the movement of the human forearm involves biceps and triceps. Figure 14.14 shows the action of both antagonistic muscles resulting in the movement of the forearm. 14.2.5

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ARM BENDING

ARM STRAIGHTENING

• When the biceps contracts, the pull force is transmitted to the radius through the tendon.

• When the triceps contracts, the pull force is transmitted to the ulna through the tendon.

• At the same time, the triceps relaxes.

• At the same time, the biceps relaxes.

• The radius is pulled upwards, causing the arm to bend.

• The ulna is pulled downwards, straightening the arm.

scapula

tendon biceps relaxes biceps contracts

tendon triceps relaxes

triceps contracts

radius

humerus elbow joint

ulna tendon

FIGURE 14.14 The action of the muscles results in the movement of the forearm

Leg movement is produced by the action of the antagonistic muscle pair. The biceps femoris is the flexor whereas the quadriceps femoris is the extensor (Figure 14.15). 1 The right calf muscle contracts, lifting the heel. The ball

of the foot pushes against the ground. 2 At the same time, the biceps femoris contracts, bending the

Brainstorm! What would happen if (a) you only have the quadriceps femoris? (b) the muscle is attached directly to the bone?

foot at the knee joint. The right leg is lifted. 3 As the right leg leaves the ground, the body weight is now supported

by the left leg which is still on the ground. The quadriceps femoris (extensor) contracts to straighten the leg. 4 The tibialis contracts to bring down the heel. As the right heel touches

the ground, body weight is shifted to the right leg. The whole sequence is repeated by the left leg.

1

biceps femoris contracts and pulls the femur 2 3

quadriceps femoris contracts, straightening the calf 4

tibialis

CHAPTER 14

calf muscle

FIGURE 14.15 The action of antagonistic muscles during walking 14.3.1

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Mechanism of locomotion in animals FISH • The fish vertebral column is flexible and can be moved from side to side by the contraction and relaxation of myotome, W-shaped muscle segments. • These antagonistic muscles act in opposite directions. This enables a fish to whip its tail. As the myotome on the right contracts, the one on the left relaxes. • The tail will be whipped to the right (Figure 14.17). • On the contrary, when the right myotome contracts, the left relaxes and the tail is whipped to the left. • Alternating waves of contraction and relaxation occur along the myotome. • The action causes parts of the body to move from side to side, pushing water backwards and sideways, and hence moving the fish forward. • The fins are used to control a fish’s movement and direction.

myotome

(b)

(a)

FIGURE 14.16 (a) Cross section and (b) longitudinal section of a fish

Tail movement pushes the fish forward

Muscles on the right side contract, pulling the tail to the right Muscles on the left side contract, pulling the tail to the left

Tail whips to the right

Tail whips to the left FIGURE 14.17 Fish locomotion mechanism

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BIRD (FLIGHT) • The action of the large and strong antagonistic muscles on a bird’s chest assist in the flapping of the wings. • The mechanism of a bird’s wing movement is shown in Figure 14.18.

wings move up

sternum wings move down pectoralis major contracts and pulls the wing down

pectoralis minor relaxes

air pressure provides upthrust pectoralis minor relaxes

pectoralis minor contracts and pulls the wing up

FIGURE 14.18 Bird’s locomotion



When the pectoralis major contracts and the pectoralis minor relaxes, the wings are pulled down.



When the pectoralis minor contracts and the pectoralis major relaxes, the wings are pulled up.

EARTHWORMS The alternate contractions and relaxations of the circular and longitudinal muscles result in a wave of peristalsis along the body of the earthworm (Figure 14.19). longitudinal muscle

CHAPTER 14

circular muscle

FIGURE 14.19 Longitudinal and circular muscles of an earthworm 14.3.2

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5

1

The posterior longitudinal muscle contracts and the circular muscle relaxes; the earthworm becomes shorter and thicker.

posterior

The posterior segment which is shortened is pulled to the front.

anterior

4

chaetae

2

The chaetae at the posterior segment anchor to the ground while the chaetae at the anterior segment release their hold of the ground.

3

The circular muscle at the anterior segment contracts and the longitudinal muscle relaxes; the earthworm becomes longer and thinner. The anterior segment (front end) extends forward.

The chaetae at the anterior segment anchor to the ground while the chaetae at the posterior segment release their hold of the ground.

FIGURE 14.20 Locomotion of the earthworm exoskeleton

extensor

exten

GRASSHOPPER (JUMP/LEAP) • The antagonistic muscles of a grasshopper, that is the flexor and extensor are attached to the inner surface of the exoskeleton (Figure 14.21).

flexor

flexor

exoskeleton

• The flexor bends a joint while the extensor straightens it.

exoskeleton

extensor

• The muscular and long hind legs of a grasshopper are adapted for jumping/leaping (Figure 14.22).

extensor

flexor

1

At rest, the flexor on the hind leg contracts, pulling the leg towards the body. In this position, the hind leg is folded into a Z shape and the grasshopper is ready to jump/leap.

2

When the extensor contracts, the hind leg is straightened backwards.

FIGURE 14.22 Locomotion of the grasshopper

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flexor

exoskeleton

FIGURE 14.21 The flexor and extensor of the hind leg

3

Subsequently, the catapult-like ejection of the hind legs projects the grasshopper forward and up into the air. 14.3.2

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Formative Practice

14.3

1 In your opinion, why do birds have hollow bones? 2 Explain how the forearm is moved upwards.

14.4

3 Explain the locomotion mechanism in fish. 4 Describe how a grasshopper performs a jump/leap.

Health Issues Related to the Human Musculoskeletal System The functions of the musculoskeletal system may be affected by disorders such as osteoporosis (Photograph 14.2), osteomalacia, arthritis and scoliosis. OSTEOPOROSIS Osteoporosis (Figure 14.23) is a bone disorder characterised by weak bones that may break easily. As a person ages, the rate of calcium loss is higher compared to the rate of calcium absorption, causing a loss in bone mass or density. Among the contributing factors are lack of exercise and low intake of calcium, phosphorus and vitamin D. Osteoporosis is common among women who reach menopause because their oestrogen level is decreased. Oestrogen is involved in calcium metabolism whereby it helps the body to absorb calcium and reduces calcium loss from the bone. A low oestrogen level can reduce bone density due to the loss of calcium from bones (Photograph 14.2).

CHAPTER 14

(a) Normal bone

(b) The bone of osteoporosis patient PHOTOGRAPH 14.2 (a) Normal bone (b) The bone of an osteoporosis patient is thinner, more brittle and porous. 14.4.1

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FIGURE 14.23 Bone mass decreases with age. The symptoms of osteoporosis include fragile bones, reduced height and stooped posture.

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OSTEOMALACIA Osteomalacia is a soft bone condition due to lack of calcium, phosphorus and vitamin D. Osteomalacia occurs among adults, especially pregnant women. It is called rickets if it occurs among children (Figure 14.24). Rickets causes the softening and weakening of children’s bones, resulting in bone defects.

(a)

normal

rickets patient

FIGURE 14.24 Normal bone and the bone of a rickets patient

(b)

ARTHRITIS

PHOTOGRAPH 14.3 (a) Normal joint (b) Deteriorating joint due to osteoarthritis

SCOLIOSIS

Activity Zone Work in a group and gather information on osteoporosis, osteomalacia, rickets, arthritis and scoliosis. Conduct a scientific study on treatments that may help individuals with health issues related to the skeletal muscle.

A common type of arthritis among the elderly is osteoarthritis. Osteoarthritis is caused by decreased synovial fluid, and wear and tear of the cartilage in certain joints (Photograph 14.3). The cartilage becomes thinner, and the ligament shortens and loses some of its elasticity. Joints, such as the knee joint becomes swollen, painful and less flexible. Arthritis restricts daily activities such as walking.

The backbone of a scoliosis patient is bent to the side, forming an ‘S’ or ‘C’ shape when viewed from the back (Figure 14.25). Scoliosis may be caused by a genetic factor or abnormal growth of the backbone during puberty development.

What is the appropriate treatment to help individuals who experience health issues related to the musculoskeletal system? The vertebral column of a normal individual

Activity Zone Build a walking aid for an individual with issues of muscle injury and joint pain.

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The vertebral column of a scoliosis patient

vertebral column FIGURE 14.25 Normal vertebral column and the vertebral column of a scoliosis patient

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Practices to maintain a healthy musculoskeletal system The following are practices to care for the musculoskeletal system. GOOD BODY POSTURE Posture refers to a person’s body position when sitting, lying, walking and standing. We should not slouch when standing or sitting. Slouching will exert pressure on the vertebral column, resulting in the misalignment of the vertebral column. This will prevent circulation of the blood, suppressing the nerves and vital organs.

Good posture when using a computer

Wear comfortable attire and shoes

PROPER ATTIRE Wear proper, comfortable and loose clothing so as not to restrict blood circulation and affect the musculoskeletal system. A suitable pair of shoes, with low heels and cushion, provides support and prevents injury to the vertebral column.

EXERCISE Exercise strengthens the joint structure and increases the flexibility of muscles and ligaments. Exercise also increases bone strength and bone mineral deposits among adults, as well as prevents osteoporosis in the elderly.

Engage in various sport activities

Kerjaya Milenia Millennial Career Orthopaedics is a specialised medical field that focuses on the diagnosis, care and treatment of the musculoskeletal system. Doctors who specialise in this field are called orthopaedic surgeons.

BALANCED DIET

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CHAPTER 14

Consume a balanced diet, especially foods rich in calcium (milk), minerals (phosphate), vitamin C and D. Vitamin D aids in calcium absorption, while vitamin C increases bone mass.

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Activity Zone Discuss the effects of the following practices on the musculoskeletal system: (a) Wearing high-heeled shoes (b) Sitting with your wallet in your back pocket (c) Carrying a heavy bag (d) Incorrect body posture when using smartphones and computers

Headache Shoulder and neck pain

Breathing difficulty and back pain

FIGURE 14.26 Effects as a result of incorrect body posture when using smartphones

Formative Practice

14.4

1 Suggest two ways to care for the musculoskeletal system. 2 As a doctor, explain ways to help scoliosis patients go through normal daily life.

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3 Define osteoporosis and explain the measures that should be adopted at a young age to prevent osteoporosis at old age. 4 Explain three practices that can help maintain a healthy musculoskeletal system. 14.4.2

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Summary SUPPORT AND MOVEMENT IN HUMANS AND ANIMALS

Types of Skeleton

Human Musculoskeletal System

Mechanisms of movement and locomotion

• Hydrostatic skeleton • Exoskeleton • Endoskeleton

Axial skeleton: skull, vertebral column, ribs and sternum

Mechanisms of movement • Human forearm (biceps and triceps) • Human leg (biceps femoris and quadriceps femoris)

Appendicular skeleton: pectoral girdle, pelvic girdle, upper and lower limbs

Joint structure: bones, cartilage, skeletal muscle, tendon, ligament, synovial membrane and synovial fluid

Mechanisms of movement in animals • Fish – myotome • Birds – pectoralis major and pectoralis minor • Earthworms – circular and longitudinal muscles • Grasshopper – flexor and extensor

Types of joints: immovable joints, slightly movable joints, freely movable joints

Health Issues

Osteoporosis, rickets, scoliosis, osteomalacia, arthritis Practices in caring for the musculoskeletal system: exercise, balanced diet, good body posture and proper clothing and shoes.

Self Reflection CHAPTER 14

Have you mastered the following important concepts? • The t ypes of skeleton in humans and animals • Axial and appendicular skeletons • Types of vertebrae in the vertebral column • Types of joints in the human skeletal system • Hinge joint structure • How humans move their arms and legs when walking • The locomotion mechanisms of animals such as earthworms, grasshoppers, birds and fish • Health issues related to the human musculoskeletal system • Practices to maintain a healthy musculoskeletal system

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Summative Practice 14 1 State the differences between cervical and thoracic vertebrae. 2 Figure 1 shows the locomotion of an earthworm.

direction of movement T segment

S segment

FIGURE 1



Explain the muscle action in segments T and S that enables the earthworm to move in the direction shown.

3 Why is it important for an organism to maintain its shape? 4 Describe the meaning of good posture. Why must we always practise good posture while doing any activity? 5 Explain why muscle contractions require adequate blood supply.

6 Figure 2 shows two types of vertebrae, X and Y in the human vertebral column. (a) Name vertebrae X and Y. (b) Explain the role of vertebrae during body movement. (c) Relate the thoracic vertebrae to the breathing mechanism.

X

Y

FIGURE 2

7 Figure 3 shows muscles P and Q, bone Y and tissue X that are involved in the forearm movement. (a) Name muscle P and Q, bone Y and tissue X. (b) State two characteristics of tissue X that enable it to function. (c) If tissue X is torn due to an accident, what problems will the victim face? (d) Suggest a suitable food for a person with fractured bone Y. In your opinion, explain why this particular food is presumed suitable for the individual.

muscle P

muscle Q

tissue X bone Y FIGURE 3

(e) Explain how all the parts labelled in Figure 3 react in the condition shown.

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Essay Questions 8 Figure 4 shows a human movement. biceps femoris quadriceps femoris calf muscle

tendon bone

knee FIGURE 4



Based on Figure 4, describe how muscles, bones, tendons, ligaments and joints enable the above movement to happen.

9 Describe how the earthworm and fish skeletal systems are adapted for locomotion in their respective habitats. 10 (a) Explain the property of muscles involved in human movement. (b) (i) Explain the measures that can be practised to maintain a healthy musculoskeletal system. (ii) Describe the factors that may put an individual at a high risk of developing osteoporosis. (c) Describe how muscles work together with the ligament and tendon to move the forearm. Enrichment 11 The long bones in mammals are not compact but hollow. Explain the advantages of hollow bones. 12 Birds fly using wings. The wing movement allows birds to exert an upthrust. However, the ability of birds to fly not only depends on its wings but also its support system. Explain how the support system helps birds to fly.

CHAPTER 14

13 The latest research in treating bone fracture includes the use of materials such as carbon nanotube that serves as a scaffolding for bone tissue growth. If you are a scientist looking for new material to treat damaged bones, what are the characteristics that the material should have in order to replace broken bones?

Complete answers are available by scanning the QR code provided

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15 CHAPTER

Sexual Reproduction, Development and Growth in Humans and Animals

Do You KNOW…

How does modern technology help in conception?

• What are the feat ures of the anatomical syste m of human reproductio n? • How is gamete fo rmed? • How does the pe riod cycle happen? • How does the de velopment of the human foetus happen?

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15.1 Reproductive System of Humans 15.1.1 Characterise the anatomy of the: • male reproductive system • female reproductive system 15.2 Gametogenesis in Humans 15.2.1 Justify the necessity of gametogenesis. 15.2.2 Describe gamete formation: • spermatogenesis • oogenesis 15.2.3 Identify the structure of: • sperm – head – middle piece – tail • Graafian follicle – secondary oocyte – follicular cells 15.2.4 Compare and contrast between spermatogenesis and oogenesis. 15.3 Menstrual Cycle 15.3.1 Analyse the changes in the levels of hormones involved during: • menstruation • follicle development • thickening of the endometrium • ovulation • corpus luteum formation 15.3.2 Correlate the changes in the levels of hormones involved with: • pregnancy • miscarriage 15.3.3 State the meaning of premenstrual syndrome and menopausal syndrome 15.4 Development of a Human Foetus 15.4.1 Describe the fertilisation process and the formation of zygotes. 15.4.2 Make a sequence and explain the early development of an embryo until implantation: • two-celled embryo • morula • blastocyst

15.4.3 Explain the role of human chorionic gonadotropin (HCG) hormone in the early stages of pregnancy. 15.4.4 Communicate about the roles of following structures in the development of a foetus: • placenta • umbilical cord 15.4.5 Justify the necessity for separate foetal and maternal blood circulatory systems. 15.5 Formation of Twins 15.5.1 Describe the processes in the formation of twins: • identical twins • fraternal twins 15.5.2 Compare and contrast identical and fraternal twins. 15.5.3 Correlate cellular division with the formation of conjoined twins. 15.6 Health Issues Related to the Human Reproductive System 15.6.1 State the meaning of impotency. 15.6.2 Communicate about causes of human impotency. 15.7 Growth in Humans and Animals 15.7.1 Explain the meaning of growth in organisms. 15.7.2 Determine parameters to measure growth in humans and animals. 15.7.3 Describe the growth of insects with exoskeleton: • complete metamorphosis • incomplete metamorphosis 15.7.4 Analyse the growth phases on sigmoid growth curves of humans and animals. 15.7.5 Analyse the intermittent growth curve of animals with exoskeletons.

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15.1

Reproductive System of Humans The male and female reproductive system The continuity of a species is dependent on the increase in population through the process of sexual or asexual reproduction. Sexual reproduction involves the production of male and female gametes by individuals who have reached sexual maturity. This process is completed with the fertilisation of both gametes to create new life. The structure and function of the male and female reproductive systems are shown in Figure 15.1 and Figure 15.2 respectively.

UTERUS •

The uterus is an organ with thick muscular walls.



The inner wall of the uterus is lined with endometrium tissue, which secretes mucus and is rich in blood vessels.



Embryo implants in the endometrium.



The endometrial tissue which is thick and rich in blood vessels supplies the embryo with nutrients and oxygen.

FALLOPIAN TUBE •

A thin, muscular tube.



The inner wall is lined with cilia.



The action of the cilium, combined with the peristalsis of the Fallopian tube, helps in delivering the secondary oocyte or embryo to the uterus.

OVARY The female reproductive organ that produces ovum (female gamete, plural: ova) and the female sex hormones, which are oestrogen and progesterone.

VAGINA A canal where sperms enter, and also serves as a passage for birth and menstruation.

CERVIX Narrow opening to the uterus which secretes mucus to help sperm swim up to the Fallopian tubes. FIGURE 15.1 Female reproductive system

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SEMINAL VESICLE Secretes fluid filled with nutrients for the sperms.

SPERM DUCT PROSTATE GLAND

Sperm is transported through the sperm duct (vas deferens).

Secretes a fluid that helps in sperm movement.

SCROTUM TESTIS

A sac-like structure that holds and protects the testis.

PENIS



Located within the scrotum.



Produces sperm (male gametes) and the male sex hormone, testosterone.

URETHRA



The male sexual organ that is rich in soft tissues and blood vessels.



Releases sperm into a female’s vagina during copulation.

A tube for the discharge of sperm and urine from the body.

FIGURE 15.2 Male reproductive system

15.1

1 State the structures of the male reproductive system.

3 State the structures of the female reproductive system.

2 Explain the functions of the seminal vesicle and the scrotum.

4 Explain the functions of the Fallopian tube and uterus.

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Formative Practice

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15.2

Gametogenesis in Humans The necessity of gametogenesis The production process of reproductive cells (gametes) is called gametogenesis. This process takes place in the gonads, which are the testes in males, and the ovaries in females. Gametogenesis produces gametes that are haploid (n). When fertilisation takes place, the nucleus of the sperm will fuse with the nucleus of the ovum in the Fallopian tube to form a diploid zygote (2n).

Spermatogenesis Spermatogenesis is a process of sperm production that takes place in the seminiferous tubules. Figure 15.3 shows a longitudinal section of the testes.

Each seminiferous tubule consists of primordial germ cells.

Primordial germ cells will undergo cell division to produce sperm. Sertoli cells within the walls of the seminiferous tubules provide nutrients throughout this process. Sperm is transported from the seminiferous tubules to the epididymis and flows out through the sperm duct (vas deferens).

sperm duct (vas deferens)

epididymis

Spermatogenesis is stimulated by the follicle-stimulating hormone (FSH) and testosterone. This process is also aided by the luteinizing hormone (LH) which stimulates testosterone secretion in the testes.

Figure 15.4 summarises the spermatogenesis scheme.

seminiferous tubules

FIGURE 15.3 Longitudinal section of the testes

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MULTIPLICATION PHASE

2n 2n

2n

2n

2n

2n 2n2n

2n 2n2n

2n spermatogonium

2n2n development

2n 2n2n

2n

Spermatogonium expands to form primary spermatocytes (diploid).

2n

GROWTH PHASE n

2n

Primordial germ cells divide mitotically to form diploid spermatogonium.

repetitive mitotic divisions

2n 2n

2n

2n

primordial germ sel

2n

2n 2n

2n

2n

2n

2n

n

2n

2n 2n

2n

n

n

n

n

2n

meiosis I

n

n MATURATION PHASE

n

secondary spermatocytes

Each primary spermatocyte undergoes meiosis I to form two secondary spermatocytes (haploid).

2n

2n 2n primary spermatocytes

2n

n n

n n

n

n n

n n n

nn

n

n

spermatid

n

n

nn

n

meiosis II

n

n

Spermatids then undergo differentiation to form sperms.

differentiation

n

n

Each secondary spermatocyte undergoes meiosis II to produce two haploid spermatids.

n

n

sperm

nn

n

nn

n

n

nn n

CHAPTER 15

n n

FIGURE 15.4 Spermatogenesis 15.2.2

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n

n

n

n

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Oogenesis Oogenesis is the process of secondary oocyte or female gamete production (Figure 15.5). This process takes place in the ovaries. Unlike spermatogenesis, oogenesis begins in a female’s ovaries before they are born. BEFORE BIRTH 1

Primordial germ cells undergo mitotic division multiple times to form oogonium (diploid).

2

Oogonium develops into primary oocyte which is encapsulated with one or more layers of follicular cells, forming primary follicles. The growth of the follicle is stimulated by the follicle-stimulating hormone (FSH). Primary oocyte then undergoes meiosis but the process stops at prophase I during fetal development.

primordial germ cell

2n

mitosis 2n

2

1

oogonium

2n development

AFTER BIRTH infant and childhood stage

primary oocytes

2n

3

every month starting from puberty until menopause

2n

primary follicle

primary oocytes

PUBERTY secondary follicle

2n meiosis I completed

5

4

Graafian follicle first polar body (n)

n

n

secondary oocytes (n) 6

ovulation sperm

n

meiosis II

8

7 n

n

n

polar bodies die

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released secondary oocyte

8 After ovulation, the remaining n

ovum

corpus luteum FIGURE 15.5 Oogenesis

follicle forms corpus luteum.

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primary follicle

secondary follicle

primary oocyte

corpus luteum Graafian follicle secondary oocyte FIGURE 15.6 Oogenesis in the ovaries 3

At birth, a baby girl already has millions of primary oocytes that remain dormant in prophase I meiosis I. The number of oocytes will decrease at puberty.

4

Upon reaching puberty, the primary oocytes will continue meiosis I to form secondary oocyte and a first polar body. Secondary oocyte will begin meiosis II which is then halted at metaphase II. The first polar body will complete meiosis II and form two second polar bodies.

5

A layer of follicular cells envelops the secondary oocyte and is called secondary follicle. The secondary follicle will then develop into the Graafian follicle, which releases oestrogen.

6

A mature Graafian follicle will approach the surface of the ovary and release a secondary oocyte into the Fallopian tube. This process is called ovulation.

7

The secondary oocyte (immature ovum) will complete meiosis II once a sperm penetrates it. Meiosis II produces ovum (n) and first polar body (n). Fertilisation takes place when the sperm nucleus fuses with ovum nucleus and produces a diploid zygote (2n). The rest of the polar bodies will die and will be disintegrated by the ovary.

upon fertilisation

9 Corpus luteum continues to grow and

without fertilisation

10

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CHAPTER 15

secretes oestrogen and progesterone. Corpus luteum and secondary oocyte degenerate and dies, and then is removed through menstruation.

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Structure of sperm and Graafian follicle A sperm has three main parts: head, midpiece and tail. The head contains a nucleus whereas the midpiece is packed with mitochondria which generates energy for the sperm to swim to the Fallopian tube for fertilisation. tail midpiece head FIGURE 15.8 Graafian follicle

follicle cells

secondary oocyte

A secondary oocyte is a large cell that is surrounded by a gel-like substance and follicular cells. The secondary oocyte and follicular cells will form the Graafian follicle.

FIGURE 15.7 Sperm

The comparison between spermatogenesis and oogenesis The comparison between spermatogenesis and oogenesis are summarised in Table 15.1. TABLE 15.1 The comparison between spermatogenesis and oogenesis

Spermatogenesis

Oogenesis Similarities

• Both are the processes of gametogenesis that take place in the reproductive organs. • Produce gametes that are haploid which are involved in fertilisation.

Differences It takes place in the testis.

It takes place in the ovaries.

Spermatogonium (diploid) produces four sperms (haploid) after meiosis.

Oogonium (diploid) only produces one functional secondary oocyte (haploid) and three nonfunctioning polar bodies after meiosis.

Sperms are smaller and made up of the midpiece, head and tail.

Secondary oocytes are large and spherical in shape.

After meiosis I, two secondary spermatocytes are produced.

After meiosis I, one secondary oocyte and one polar body is produced.

Meiosis is completed.

Meiosis II is only completed when a sperm fertilises the secondary oocyte.

Spermatids undergo differentiation to become sperms.

Secondary oocyte does not undergo differentiation.

The production of sperm is continuous from puberty until old age.

The production of the secondary oocyte is not continuous. It starts in the female foetus and remains dormant when the baby is born. The process continues once the female reaches puberty and stops during menopause.

Millions of sperms are formed every day.

Only one secondary oocyte is released from the ovaries at every menstrual cycle.

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Formative Practice

15.2

1 What could possibly happen if gametogenesis does not take place?

15.3 Biological Lens One of the side effects of low oestrogen is calcium loss in the body which leads to a reduction in bone density, making it porous and weak. This condition is called osteoporosis.

2 Explain three differences between spermatogenesis and oogenesis.

Menstrual Cycle Role of hormones in menstrual cycle MENSTRUAL CYCLE The menstrual cycle involves the production of a secondary oocyte and thickening of the endometrial wall throughout one cycle. In this cycle, the endometrium will become soft, thick and rich with blood vessels. This is to prepare the endometrium for embryo implantation. If fertilisation does not take place, the secondary oocyte will die and the endometrium wall will shed. This will lead to bleeding known as menstruation.

The functions of hormones in a menstrual cycle is shown in Table 15.2. TABLE 15.2 Functions of hormones in a menstrual cycle

Gland

Hormone

Pituitary

Folliclestimulating hormone (FSH)

Function • Stimulates follicle growth in the ovary. • Stimulates the release of oestrogen. • Stimulates ovulation.

Luteinizing hormone (LH)

MillennialMilenia Career Kerjaya

• Stimulates the release of progesterone. • Repairs and stimulates the thickening of the endometrium.

Ovary Oestrogen

• Stimulates follicle growth until it matures. • Stimulates FSH and LH release prior to ovulation.

Progesterone

• Stimulates the thickening of the endometrium, making it thick, folded and rich in blood vessels to prepare for the implantation of embryo. • Stops the release of FSH and LH to prevent follicle growth and ovulation.

Changes in hormonal level, follicle growth, and changes in endometrial wall thickness throughout one menstrual cycle are shown in Figure 15.9. 15.3.1

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Obstetricians and gynaecologists are specialists in female reproduction and women’s health.

• Causes the formation of the corpus luteum.

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HORMONE LEVEL hormone level LH

progesterone

oestrogen FSH

1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 days

FOLLICLE DEVELOPMENT secondary oocyte

Graafian follicle

Development of primary follicle

Development of secondary follicle/

Ovulation

Corpus luteum

Corpus luteum degenerates

CHANGES IN ENDOMETRIAL THICKENING

Menstruation

Days of menstrual cycle FIGURE 15.9 Stages of events and hormonal level changes in one menstrual cycle

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DAY 0–5 • Before a menstrual cycle begins, the level of hormones is low. With the absence of stimulation from progesterone and oestrogen, the thickened endometrium will shed and menstruation will begin (first day). • A menstrual cycle begins a day before menstruation when the hypothalamus releases the gonadotrophin-releasing hormone (GnRH). • GnRH stimulates the pituitary gland to release the follicle-stimulating hormone (FSH) and luteinizing hormone (LH) into the blood. • FSH stimulates follicle growth in the ovary. Within the primary follicle, the oocyte grows into the secondary oocyte, which is contained within the Graafian follicle. • Growing follicles release oestrogen. • Oestrogen encourages follicle maturation and also encourages endometrial wall repair. • Low levels of oestrogen inhibit the release of FSH and LH via a negative feedback mechanism, which in turn prevents the growth of new follicles.

DAY 6–14 • Oestrogen level rises and peaks on day 12, stimulating the hypothalamus to secrete GnRH via a positive feedback mechanism. • A high level of GnRH then stimulates the pituitary gland to secrete more FSH and LH. • The LH level rises until it peaks on day 13, leading to ovulation and release of a secondary oocyte from Graafian follicle on day 14. • LH also stimulates the follicular tissue left behind to transform into the corpus luteum.

DAY 15–21 • LH stimulates the corpus luteum to secrete oestrogen and progesterone. • The combination of oestrogen and progesterone inhibits the release of FSH and LH from the hypothalamus via negative-feedback mechanism so as to stop the growth of new follicles. • Progesterone stimulates endometrial wall thickening, enriching it with blood vessels in preparation for embryo implantation, in the event that fertilisation takes place.

DAY 22–28 • If fertilisation does not take place, decreasing LH levels will cause the corpus luteum to degenerate, which in turn stops the secretion of oestrogen and progesterone. • Without stimulation from oestrogen and progesterone, the endometrium will shed and menstruation will begin. • Low levels of progesterone and oestrogen will no longer inhibit the hypothalamus and pituitary gland, making way for GnRH to be secreted again, which then stimulates secretion of FSH and LH. A new menstrual cycle will begin with new follicle growth. CHAPTER 15

• If fertilisation occurs, the corpus luteum will continue to grow and secrete progesterone and oestrogen. • This will cause the endometrial wall to continually thicken in order to support foetal growth.

15.3.1

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Role of hormone in pregnancy and miscarriage The corpus luteum will continue to produce oestrogen and progesterone up to three to four months after pregnancy. Thereafter, the corpus luteum will degenerate, and the production of oestrogen and progesterone will be taken over by the placenta until birth. Progesterone inhibits the secretion of FSH and LH. Therefore, the menstrual cycle and ovulation do not occur throughout a Fatigue pregnancy. The imbalance of progesterone and oestrogen levels may lead to a miscarriage, due to the decrease of progesterone Headache level which causes the uterus to shrink. Emotional instability

Premenstrual syndrome and menopausal syndrome

Bad temper

PREMENSTRUAL SYNDROME (Photograph 15.1) Premenstrual syndrome or symptoms that appear prior to a menstrual cycle usually manifests between 7 to 14 days before the first day of the menstrual cycle. This syndrome occurs due to the imbalance of oestrogen and progesterone hormones within the menstrual cycle. PHOTOGRAPH 15.1 Premenstrual syndrome symptoms

MENOPAUSE (Photograph 15.2)

Difficulty sleeping

Menopause occurs within the ages of 46 to 50 years old, when ovulation and menstruation stop naturally. The increase in age leads to reduced secretion of progesterone and oestrogen, which then causes reduced stimulation of FSH and LH on the ovaries. At this stage, the ovaries stop producing ovum. After menopause, a woman is not able to conceive a child anymore.

Hot flushes

Low mood Bad temper

PHOTOGRAPH 15.2 Menopausal symptoms

Formative Practice

15.3

1 State the hormones involved in the menstrual cycle and their functions. 2 Explain the functions of progesterone and its effects on pregnancy.

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3 Explain what would happen to the corpus luteum if fertilisation does not occur. 4 In your opinion, what is the best way to overcome premenstrual syndrome?

15.3.2

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15.4 Biological Lens

Development of a Human Foetus The process of fertilisation Fertilisation can occur when one out of the millions of sperm succeeds in penetrating the secondary oocyte in the Fallopian tube. This is followed by changes to the secondary oocyte’s membrane that prevents penetration from other sperms. Then, fertilisation occurs when the sperm nucleus fuses with the ovum nucleus to form a diploid zygote.

Each semen ejaculation contains between 300 to 500 million sperms. However, only about 300 to 500 sperms successfully reach the secondary oocyte in the Fallopian tube.

Early development of an embryo until implantation While travelling down the Fallopian tube, the zygote undergoes multiple divisions through mitosis.



The first cell division produces a two-cell embryo. The following cell divisions will finally produce a morula.



The morula then transforms into a blastocyst (Figure 15.10).



The blastocyst will then implant in the endometrium. This process is called implantation. The blastocyst continues to grow into an embryo.

zygote 2 cells

fertilisation

4 cells

morula

8 cells

blastocyst

ovary unfertilised secondary oocyte

implantation of the blastocyst

endometrium

CHAPTER 15

AR



the thickened blastocyst wall will develop into embryo FIGURE 15.10 Early development of an embryo and implantation of a blastocyst 15.4.1

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Role of human chorionic gonadotropin (HCG) hormone The placenta also produces the human chorionic gonadotropin (HCG) hormone during pregnancy. The level of this hormone increases at the early stages of pregnancy and will double every two to three days for the first four weeks of pregnancy. The main function of HCG is to ensure that the corpus luteum continues to secrete oestrogen and progesterone in the early stages of pregnancy. This hormone can be detected in the urine of pregnant mothers.

Role of placenta and umbilical cord in foetal development PHOTOGRAPH 15.3 Pregnancy test detects HCG in urine

The placenta is formed from the mother’s endometrial tissue and embryonic tissue. It is connected to the foetus through the umbilical cord which contains blood vessels that carries substance in and out of the foetus. The umbilical cord is a tube that contains the umbilical vein and umbilical arteries. • The umbilical vein carries blood rich in oxygen and nutrients from the placenta to the foetus. • Umbilical arteries carry deoxygenated blood (rich in carbon dioxide) and nitrogenous waste such as urea from foetus to the placenta. foetal blood vessels

placenta

maternal blood foetal blood capillaries umbilical cord

umbilical vein umbilical arteries placenta FIGURE 15.11 Placenta and umbilical cord

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Importance of placenta The placenta is the exchange site of substances between mother and foetus. •

Glucose, amino acids, hormones, antibodies and oxygen are absorbed from the mother’s blood into the foetal blood capillaries.



Carbon dioxide and nitrogenous waste such as urea are absorbed from the foetal blood capillaries into the mother’s blood circulation.

The placenta also acts as an endocrine organ that secretes hormones during pregnancy. •

In the fourth month of pregnancy, the corpus luteum will degenerate and no longer secrete progesterone.



The placenta will replace corpus luteum in producing progesterone and oestrogen needed to maintain endometrial thickness.

Foetal and maternal blood circulatory systems The blood of the mother and the foetus do not mix as they are separated by a thin membrane. This is important because: (a) It protects the foetus from certain dangerous chemical substances such as toxins and bacteria that can be absorbed into the foetal blood circulation. (b) It prevents the thin foetal blood vessels from bursting due to the mother’s high blood pressure. (c) It prevents agglutination or blood clots from happening in the foetus, as the foetus might not be of the same blood group as the mother. The thin membrane layer is not able to prevent certain substances from being absorbed, such as drugs and medication, cigarette smoke and alcohol ingested by the mother. Viruses such as HIV and rubella can also cross the placenta and be absorbed into the foetal blood circulation, which may disrupt the foetal development.

15.4

1 Explain the early developmental process of the embryo. 2 What is the main function of the HCG hormone? 15.4.4

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3 Describe the function of the placenta. CHAPTER 15

Formative Practice

4 State what might happen if maternal blood mixes with foetal blood.

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15.5

Formation of Twins Process of twin formation Twins refer to two or more children that are born from one pregnancy. There are two types of twins: • identical twins • fraternal twins

(a) IDENTICAL TWINS

1 placenta shared with 2 foetus

1 placenta shared with 2 foetus

one sperm fertilises one ovum

embryo divides into two

(b) FRATERNAL TWINS

separate placentas

2 sperms 2 ova

two sperms fertilise two ova

two separate embryos are formed

FIGURE 15.12 Development of (a) identical twins and (b) fraternal twins

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TABLE 15.3 Differences between identical and fraternal twins

Differences between identical and fraternal twins Identical twins

Fraternal twins

Product of fertilisation of one ovum and one sperm forming one zygote.

Product of fertilisation of two sperms and two ova forming two zygotes.

Embryo divides into two.

Embryo does not divide into two.

One placenta is shared between two foetus.

Each foetus has its own placenta.

The genetic makeup and physical appearances of these twins are similar as they are from the same zygote.

The genetic makeup and physical appearances of these twins are different as they are from two different zygotes.

The sex of both twins is the same.

The sex of both twins may be the same or different.

Development of conjoined twins Conjoined twins develop when there is incomplete division of the embryo in identical twins. Although two foetuses are formed from the embryo, some of their physical parts are still fused together, usually the chest, abdomen or buttocks. Conjoined twins may also share one or two internal organs. The life of conjoined twins may be difficult as they must always be together. They also do not have any time alone. Their movements are limited due to their physical state. Most conjoined twins die before they are born or have short lifespans. They may be able to be separated through surgery. However, the success of surgery depends on the joined part and what internal organs are shared between them. PHOTOGRAPH 15.4 Conjoined twins

Formative Practice

15.5

1 State two differences between identical and fraternal twins. CHAPTER 15

2 State the characteristics of conjoined twins.

15.5.2

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15.6

Health Issues Related to the Human Reproductive System Impotency Impotency occurs when a husband and wife are unable to conceive. The cause of this might be from the husband or wife, or both. Erectile dysfunction

Testes do not produce sperm

CAUSES OF MALE IMPOTENCY

Low quality sperm/ abnormal sperm

Hormonal imbalance

Low sperm count

FIGURE 15.13 Causes of male impotency

Ovaries do not produce secondary oocyte

Blocked Fallopian tubes

CAUSES OF FEMALE IMPOTENCY

Abnormal uterus

Video: IVF (Accessed on 21 August 2019)

What are the benefits and drawbacks of science and technological contributions to human reproduction? What moral issues are related to the application of technological reproduction? Discuss.

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Growth in the uterus

FIGURE 15.14 Causes of female impotency

ICT 15.1

Activity Zone

Hormonal imbalance

TREATMENT FOR IMPOTENCY •

Hormonal imbalance can be treated with hormonal therapy.



Blocked Fallopian tubes or blocked sperm ducts can be treated via surgery.



In vitro fertilisation (IVF) can be used for women who have blocked Fallopian tubes.

Formative Practice

15.6

What are the causes of impotency? 15.6.1

15.6.2

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15.7

Growth in Humans and Animals

Growth in organisms Growth in organisms is an irreversible, permanent process that involves the increase in the number of cells, size, volume and weight of the organism’s body. Growth also involves differentiation and cell specialisation as well as specialising the shapes and functions of cells. Growth in organisms is important for the development and maturation of bodily systems.

Measuring growth in humans and animals The parameters that are used in measuring growth are: (a) Increase in size or volume, for example, changes in height or length of an organism (b) Changes in fresh weight or dry weight: (i)  Dry weight refers to the weight of an organism after all the fluid is removed from its body. This is done by weighing the organism after it has been dried in the oven at 100 °C repeatedly until the weight remains the same. The weakness of this parameter is that the organism has to be killed. However, this method is suitable for plants. (ii) Fresh weight can be taken whenever and organisms do not need to be killed. However, this method is less accurate because the amount of fluid in the body is dependent on the organism’s fluid intake. This parameter is measured for a certain amount of time.

Growth of Insects

CHAPTER 15

Organisms with exoskeletons like insects undergo growth differently. Insects go through two different types of growth which are complete metamorphosis and incomplete metamorphosis.

15.7.1

15.7.2

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15.7.3

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Insects like butterflies undergo complete metamorphosis. In complete metamorphosis, there are four different stages of growth, which are egg, larvae, pupa and adult. Figure 15.15 shows complete metamorphosis.

The butterfly matures into an adult butterfly. adult butterfly egg

COMPLETE METAMORPHOSIS A butterfly emerges from the pupa with soft and folded wings.

caterpillar (larvae)

pupa

Rapid development at this stage.

A caterpillar hatches from an egg and eats leaves to grow. The caterpillar starts to become a pupa. FIGURE 15.15 Complete metamorphosis

Grasshoppers undergo incomplete metamorphosis, where the insect undergoes a few stages of ecdysis before becoming an adult. Figure 15.16 shows incomplete metamorphosis. Nymph (young insect) hatches from egg egg nymph

INCOMPLETE METAMORPHOSIS

casts off outer cuticle during ecdysis

nymph

adult grasshopper

ecdysis

Ecdysis occurs a few more times until the insect becomes an adult

FIGURE 15.16 Incomplete metamorphosis

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Growth phases in sigmoid growth curves of humans and animals The growth curve is achieved by plotting growth parameters against time (Figure 15.17). Most organisms’ growth curves show a similar pattern that is a sigmoid curve (S-shaped). Growth occurs gradually and continuously. There are six phases in the sigmoid growth curve, which are the lag phase, exponential phase, stationary phase, maturity phase, senescence and death phase.

LAG PHASE The growth rate is low because it involves little cell division and cell elongation.



It is the phase of adjustment to new sources available in the environment.

Exponential Phase

Stationary Phase

Maturation Senescence Death Phase Phase Phase

growth



Lag Phase

EXPONENTIAL PHASE •

Highest growth rate.



Cell division and elongation occurs actively.



Organism’s size increases rapidly.

STATIONARY PHASE •

Growth rate slows down and occurs at a constant rate.



Cells reach maximum size.



Cells undergo differentiation to form specialised cells.

time FIGURE 15.17 Sigmoid growth curve

MATURITY PHASE •

Organism reaches maturity.



Zero growth rate.



The rate of cell division is similar to the rate of cell death.



Cell division only happens to replace impaired or dead tissues.

SENESCENCE PHASE •

Negative growth rate.



Organism goes through ageing.

CHAPTER 15

DEATH PHASE Ageing, illness, lack of nutrients or space eventually leads to death of an organism.

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Intermittent growth curve of animals with exoskeletons ICT 15.2 Video: Insect ecdysis (Accessed on 21 August 2019)

Insects such as grasshoppers have an exoskeleton made up of chitin. The exoskeleton does not grow proportionately with the growth of the insect. To allow growth and development, animals with exoskeletons must shed their hard exterior. The moulting process of the exoskeleton that allows growth and development of insects is called ecdysis. This process is controlled by hormones.

• The process of ecdysis happens periodically. Polar growth is not continuous and is intermittent (Figure 15.18).

body length (cm) adult instar V instar IV

• The horizontal part of the graph indicates zero growth. At this stage, known as instar, the insect is not increasing in length.

ecdysis instar III

• The vertical lines of the graph represent rapid growth.

instar II

• At this stage, the nymph undergoes ecdysis and its size increases rapidly • Ecdysis occurs multiple times until the insect reaches adulthood.

ecdysis

instar I

ecdysis

ecdysis

egg ecdysis

FIGURE 15.18 Growth curve of animals with exoskeletons

time (day)

HOW DOES ECDYSIS HAPPEN? • A new exoskeleton forms underneath the old exoskeleton • B  efore the new exoskeleton hardens, the insect will increase its volume by sucking in air to expand its body • T  his action breaks the old exoskeleton and the insect with its new exoskeleton will emerge • T  he insect will expand its body one more time before the new exoskeleton hardens

PHOTOGRAPH 15.5 A cicada emerging from its old exoskeleton

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The stages between ecdysis are called instar and at this stage, the insect is known as a nymph. During instar, the insect is actively building tissue and increasing body volume. 15.7.5

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Formative Practice

15.7

1 Describe how to measure growth in animals.

3 Explain the event that happens during the exponential phase.

2 Explain the differences between complete and incomplete metamorphosis.

4 Why must insects go through ecdysis?

Summary SEXUAL REPRODUCTION, DEVELOPMENT AND GROWTH IN HUMANS AND ANIMALS

• Male reproductive system • Female reproductive system

Gametogenesis

Development of Human Foetus

• Spermatogenesis and oogenesis • Gamete structure: sperm and secondary oocyte • Comparison between spermatogenesis and oogenesis

• Fertilisation process and the formation of zygotes • Role of placenta and umbilical cord in the development of a foetus • Necessity for separate foetal and maternal blood circulatory systems

Menstrual Cycle • Changes in the levels of hormones during: – menstruation – follicle development – thickening of the endometrium – ovulation – corpus luteum formation • Changes in the levels of hormones during: – pregnancy – miscarriage • Premenstrual syndrome and menopausal syndrome

Formation of Twins • Identical twins • Fraternal twins • Conjoined twins

Health Issues Related to the Human Reproductive System

Causes of human impotency Growth in Humans and Animals

• Growth of insects with exoskeleton: – complete metamorphosis – incomplete metamorphosis • Sigmoid growth curves of humans and animals • Intermittent growth curve of animals with exoskeletons

CHAPTER 15

Reproductive System of Humans

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Self Reflection Have you mastered the following important concepts? • Male and female reproductive systems • Spermatogenesis and oogenesis • Gamete structure • Changes in hormone level, follicle growth, endometrial thickening, ovulation and corpus luteum formation within the menstrual cycle • Changes in hormone level in a pregnancy and a miscarriage • • • • • • • • •

Premenstrual syndrome and menopause Fertilisation process until the formation of zygote Early embryo development until implantation Role of human chorionic gonadotropin (HCG) hormone during early pregnancy Fetal and maternal blood circulation Formation of t wins (identical, fraternal, conjoined) Health issues related to the human reproductive system Sigmoid growth cur ve of humans and animals Growth of insects (complete and incomplete metamorphosis)

Summative Practice 15 1 What causes the premenstrual syndrome in some women? 2 State the differences between the formation of identical and fraternal twins. 3 The foetus has its own blood circulation system, separate from its mother. Explain why. 4 (a) A pair of identical twins were separated at birth. Once they reached adulthood, they found out that they both have different body sizes. Explain the factors that would cause this. (b) Explain why pregnant mothers must stop smoking.

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5 State the changes that occur to a zygote from fertilisation up to birth. 6 A woman took contraceptive pills to prevent pregnancy. The pill inhibits secretions of the Follicle Stimulating Hormone (FSH) from the pituitary gland. Explain the effects of taking contraceptive pills on the menstrual cycle. 7 Figure 1 shows the hormonal regulation of a menstrual cycle.

pituitary gland hormone X

hormone Y

structure T ovulation hormone Q

primary follicle hormone P hormone level

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 days FIGURE 1

(a) State the effect on ovum development if hormone X is not enough. (b) Explain the effects of hormone P and hormone Y imbalance. (c) Based on Figure 1, describe the relationship between changes in structure T with the level of hormone P and hormone Q. (i) from day 16 to day 24 (ii) from day 24 to day 28 8 Figure 2 shows a human foetus inside a uterus. (a) Name the structures labelled P and Q. (b) Explain the blood composition that flows through the blood vessel at Q.

P

Q

(c) Explain the function of structure P. (d) (i) State the types of immunity a foetus can inherit from its mother. (ii) Explain how structure P helps in foetal immune response.

CHAPTER 15



FIGURE 2

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Essay Questions 9 A woman having problems getting pregnant needed an injection of hormone X from a specialist. Hormone X has the same function as the luteinizing hormone (LH). After a certain period, the woman was pregnant. Explain how the hormone X injection can help the woman to get pregnant. 10 (a) Describe the process of sperm production in the testes. (b) Figure 3 shows the formation of two sets of twins. Compare the formation of the twins R and S. Enrichment 11 During ejaculation, approximately 300 million sperms are released. From this amount, only about 300 sperms arrive at the secondary oocyte, and only one will be successful in fertilising the ovum. If only one sperm reaches the secondary oocyte, fertilisation will not take place. Explain why.

R

S FIGURE 3

12 Describe how changes in different hormone levels in one menstrual cycle prepare a woman for pregnancy. 13 The umbilical cord is the lifeline between the foetus and its mother. Cord blood is blood left in the umbilical cord and placenta after birth. After a baby is born, cord blood is kept as it is a source of stem cells rich in hematopoietic stem cells. Is it important for parents to keep the cord blood for their children’s future?

Complete answers are available by scanning the QR code provided

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Glossary Active transport—The movement of

substances across the membrane of living cells, against the concentration gradient with the help of carrier proteins and energy from ATP.

aerobic respiration—The complete oxidation of glucose to carbon dioxide, water and energy by using oxygen. anabolism—The metabolic process that synthesises complex molecules from simpler molecules. The process requires energy. anaerobic respiration—The incomplete oxidation of glucose without the use of oxygen or in limited oxygen supply. appendicular skeleton—The part of the skeleton that consists of the pectoral and pelvic girdle, leg bones and arm bones. axial skeleton—The part of the skeleton that consists of the skull, vertebral column, sternum and rib cage. Forms the main axis of the body.

Balanced nutrition—Food nutrition that

contains all nutrients in the right amount to fulfill the requirements of the body.

biohazard—Any chemical or biological agent that poses a threat or risk to humans and the environment. blastocyst—The early developmental stage of mammalian embrio that consists of a ball of cells with a hollowed centre that is filled with fluid. bolus—The ball of chewed food that has been mixed with saliva, formed in the mouth through the action of the tongue before being swallowed.

Carbaminohemoglobin—A compound that

consists of carbon dioxide and the pigment haemoglobin in the blood.

catabolism—The metabolic pathway that breaks down complex molecules into simpler molecules. The process releases energy. crenation—The shrunken state of animal cells when the surrounding solution is hypertonic towards the cytoplasm of the cells.

Deamination—The removal of an amino group from an amino acid.

dendrite—The nerve fibre that receives impulses from adjacent neurons and transmits them towards the cell body. deoxyribonucleic acid (DNA)—Nucleic acid that carries the genetic codes of an organism and is the main component of chromosomes. diploid—Describes two sets of chromosomes, one set from the male parent and another set from the female parent.

Effector—Parts of the body that receive

instructions from the control centre and respond to the stimuli accordingly.

embryo—The early developmental stage of zygote in seeds (in plants), eggs (in animals), or uterus (in humans and animals). emphysema—A condition where the air sacs in the lungs are damaged and cause difficulties in breathing. enzyme—The organic catalyst, normally proteins, that catalyse biochemical reactions in living cells.

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Gametogenesis—The process of male and female gametes formation in the reproductive organ.

Golgi apparatus—A cellular component in the cytoplasm that processes, packs, and distributes secretory substances such as enzymes and proteins. Graafian follicle—Mature follicle in the ovary that contains secondary oocyte and produces the hormone oestrogen.

Haemoglobin—Protein in the red blood cell that functions to transport oxygen.

haemophilia—Blood disease that causes the patient’s blood clotting to be impaired due to the lack of clotting factors. homeostasis—The regulation of the internal environment of organisms so that physiological processes can proceed at the optimum level.

Meiosis—The cell nucleus division that produces four haploid daughter cells.

mitosis—The cellular division that produces two daughter cells that contain a similar number and type of chromosome as the parent cell. morula—A solid ball of cells during the development of embryo before the blastocyst stage. Nephron—The functional unit in the kidney that consists of the glomerulus, Bowman capsule, convoluted tubule, Henle loop and collecting duct. neuron—Cells in the nervous system that consists of the axon, cell body and dendrites. nucleic acid—A complex organic compound in living cells that consists of nucleotide chains. There are two types of nucleic acid, which are DNA and RNA.

hormone—Chemical substances that regulate specific functions in the body.

nucleotide—The basic unit of DNA molecule that contains phosphate group, ribose or deoxyribose, and a nitrogenous base.

Immunity—The body’s ability to fight infectious

nucleus—The largest cellular component in the cell that contains genetic materials. The nucleus acts as the control centre for the cell.

implantation—The adhering of the embryo (at the blastocyst stage) to the wall of the uterus.

Oogenesis—The formation of the ovum in the

diseases carried by pathogens.

insulin—Hormone that stimulates the conversion of glucose to glycogen in the liver and muscle cells.

Ligament—Elastic tissues that connect bone to bone.

lysosome—Membrane-bound sacs that contain enzymes that digest substances in the food vacuole.

ovary.

organism—Living things that are capable of conducting living processes such as feeding, growing, reproducing and breathing. osmosis—The diffusion of water molecules from a region of higher water potential towards a region of lower water potential, across a selectively permeable membrane. oxyhaemoglobin—A compound that is formed when oxygen combines with haemoglobin in erythrocytes.

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Pathogen—The microorganisms that carry infections and diseases.

phloem—The vascular tissue that is involved in the transport of food materials from the site of photosynthesis to other parts that need them. placenta—The organ that forms from the tissue of the foetus and the mother to allow for material exchanges between the foetus and the mother. plasmolysis—The shrinking of cytoplasm from the plant cell wall as a result of water loss through osmosis.

smooth muscle—Non-striated muscles that can be found in intestinal walls and blood vessels. spermatogenesis—The formation of sperm in the testis. sternum—The bone in the middle section of the vertebrate chest. synapse—A site between two nerve cells, or neurons and effector to communicate.

Telophase—The final stage in cell division,

when the nuclear membrane envelopes the nucleus of each daughter cell.

platelet—Fragments of cell cytoplasm in the blood that contain no nucleus and are involved in blood clotting.

tendon—Flexible non-elastic tissue that joins the muscle to the bone.

Receptor—Specialised sensory cells that

Ultrafiltration—The filtration process of blood

reflex arc—The stimulus pathway that triggers reflex responses. The pathway consists of receptors, control centres and effectors.

Vacuole—Sacs that contain cell sap that can

detect stimuli.

plasma that contains dissolved nutrients, across the wall of blood capillary.

be found in the cytoplasm.

Sacrum—The triangular bone in the hip area of

vertebra—Small bones that form the spine

skeletal muscle—Muscles that connect a bone to another bone. The movement of the skeleton relies on the contraction of skeletal muscles.

Zygote—The union of the ovum (female

the vertebral column.

gamete) and sperm cell (male gamete) during fertilisation.

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References Abdullah, H.R. (2006, Jan 6). Sweet hope for diabetics. The Star Online. Retrieved from https://www.thestar.com. my/news/nation/2006/01/06/sweet-hopes-for-diabetics/. Audesirk, T., Audesirk, G. & Byers, B.E. (2017). Biology: Life on Earth. London: Prentice-Hall International (UK) Ltd. Boyle, M. (2014). IB Science Skills Biology. New York: HarpersCollins Publishers Limited. Green, N.P.O., Stout, G.W., & Taylor, D.J. (1997). Biological Science 1 & 2, (3rd Ed). Cambridge, UK: Cambridge University Press. Hussin, M. (2015, May 5). Racun botani kawal siput gondang. MyMetro. Retrieved from https://www.hmetro.com. my/node/48690. Hussin, M. (2016, Oct 25). Racun botani gondang emas. MyMetro. Retrieved from https://www.hmetro.com.my/ node/176702. HIV and AIDS Data Hub for Asia-Pacific. (2018). HIV AIDS Asia Pacific Research Statistical Data Information (Malaysia). Retrieved from https://www.aidsdatahub.org/Country-Profiles/Malaysia Institut Jantung Negara. Retrieved from www.ijn.com.my International Invention, Innovation & Technology Exhibition (ITEX). (2018). Congratulations to all winners. Retrieved from https://itex.com.my/2018/06/01/congratulations-to-all-winners/ ITMO-developed nanoparticle technology helps stop internal bleeding. (2018, Feb 27). ITMO. NEWS. Retrieved from http://news. ifmo.ru/en/science/new_materials/news/7344/ Jones, M. (2009). Biology. Heinemann: Pearson Education Limited. Junus, L. (2018, Jun 25). MyThrob pantau jantung. Utusan Online. Retrieved from https://www.utusan.com.my/ sains-teknologi/sains/mythrob-pantau-jantung-1.696165 Mackean, D.G. (2000). IGCSE Biology. London, UK: John Murray (Publishers) Ltd Maders, S.S. (2001). Biology. New York: The McGraw-Hill Companies. Reece, J.B., Urry, L.A., Cain, M.L., Wasserman, S.A., Minorsky, P.V., & Jackson, R.B. (2011). Campbell Biology. (9th Ed). San Francisco, Cal.: Pearson Benjamin Cummings. Solomon, E.P., Berg, L.R., & Martin, D.W. (2002). Biology. US: Thomson Brooks/Cole. Solomon, E.P., Martin, C., Berg, L.R., & Martin, D.W. (2014). Biology. (9th Ed). US: Thomson Learning. Taguling, N. K. (2015). Effect of combined plant extracts on golden apple snail (Pomacea canaliculata (Lam.)) and giant eartworm (Pheretima sp). International Journal of Agriculture and Crop Sciences, 8(1), 55-60. UNAIDS. (2018). Global HIV & AIDS statistic. Retrieved from https://www.unaids.org/en/resources/fact-sheet. Williams, G. (2011). New Biology for You. Cheltenham, UK: Nelson Thornes Ltd.

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Form 4 Biology This textbook has been written based on the Dokumen Standard Kurikulum dan Pentaksiran (DSKP) for Biology Form 4, published by the Ministry of Education, Malaysia. It is guided by the concepts of Scientific Skills, Science Process Skills, Higher Order thinking Skills, 21st Century Skills and the STEM teaching and learning approach. The objective of this textbook is to develop well-rounded pupils and to equip them with the skills needed for the 21st century.

Icons in the Text Book and their Functions

Biological Lense Additional information related to theories and concepts

Our World of Biology

Higher-order thinking questions which cover applying, analysing, evaluating and creating questions

Illustrates the application of theories and concepts learnt in everyday life

Brainstorm! Challenges pupils to think critically and creatively

Malaysian Innovation The successes of Malaysian scientists and the related scientific and technological developments in Malaysia

Take Note! Reminders for students when carrying out activities or experiments

Questions to test pupils’ understanding at the end of every subtopic

Summative Practice Questions to test pupils’ understanding at the end of every chapter

Kerjaya Milenia Millennial Career Describes careers related to a concept or topic

Summary A summary of the main concepts

STEM Bulletin Highlights current developments in the related fields of science and technology

Across the Fields Shows the connection between biology and other fields

Activity Zone Suggested activities for pupils to carry out

Self Reflection A checklist on the mastery of concepts for pupils’ reference 4.2.3

Learning Standard based on the Form 4 Biology Dokumen Standard Kurikulum dan Pentaksiran (DSKP)

Author’s Biodata

Gan Wan Yeat Born on 30th May 1966 in Jasin, Melaka. She is currently the Senior Administrative Assistant at SMK (P) TAMAN PETALING. A graduate with Bachelor (Honours) of Microbiology and Master of Education (Psychology) from Universiti Malaya, she has been teaching Biology and Science since 1994. She is also the author for the KSSM Biologi Tingkatan 4 and 5 textbooks and other Biology and Science reference books.

Nor Azlina binti Abd. Aziz Born on 14th November 1967 in Muar, Johor. She is a senior lecturer at The Centre for Foundation Studies, Universiti Malaya, Kuala Lumpur. She teaches Biology specialising in the fields of cellular biology and genetics. She holds a Doctor of Philosophy (PhD) in animal breeding technology, a Master of Philosophy (Mphil) in health and biomedical science, and a Bachelor of Science in genetics from Universiti Malaya. She also holds a Diploma in translation from DBP and has over 15 years’ experience in translating and editing.

Yusmin binti Mohd. Yusuf Born on 15th June 1969 in Alor Setar, Kedah. She is a senior lecturer at The Centre for Foundation Studies, Universiti Malaya, Kuala Lumpur. She earned a Doctor of Philosophy from Universiti Malaya, in human genetics and has been teaching biology for almost 20 years. She is now teaching biology at The Centre for Foundation Studies, while also supervising postgraduate students. She specializes in biotechnology and genetic engineering.

Noor Haniyatie binti Ibrahim Born on 21st April 1984 in Selangor. She is a Biology teacher in SMK Seksyen 3 Bandar Kinrara, Puchong, Selangor. A graduate with a Bachelor of Science in Education (Biology) from Universiti Pendidikan Sultan Idris, Tanjung Malim, she started her career as a teacher in 2008 at SMK Dato Onn, Batu Pahat, Johor and continued for 11 years before she was transferred to her current school. She has given many talks on techniques in answering the SPM Biology paper and is also an experienced writer of several learning modules and workbooks before becoming an author of the KSSM Biologi Tingkatan 4 textbook.

The publisher has made some amendments on the following pages. Any inconvenience caused is much regretted.

PAGE 49

3.2

CHAPTER 3

Concept of Movement of Substances Across a Plasma Membrane The characteristics of substances that are able to move across a plasma membrane There are three common factors that determine whether a molecule can pass through a plasma membrane, which are molecule size , polar molecule and ionic charge.

ICT 3.3 Video: Movement of molecules and ions across the plasma membrane (Accessed on 21 August 2019)

CHARACTERISTICS OF MOVEMENT OF SUBSTANCES ACROSS A PLASMA MEMBRANE

Nonpolar molecules

SMALL MOLECULE AND ION

Examples: • Fatty acid • Glycerol • Fat soluble vitamins (A, D, E, K) • Steroid compounds

LARGE MOLECULE

• Polar molecules (Example: water)

Examples:

• Nonpolar molecules (Examples: oxygen, carbon dioxide)

• Glucose • Amino acid

• Ion (Examples: K+, Na+, Ca2+, Mg2+)

small molecule and ion

lipid soluble molecule

small nonpolar molecule

Extracellular

H2O

O2

CO2

large molecule

carrier protein H2O

O2

Cytoplasm

CO2

channel protein

FIGURE 3.3 Movement of substances across a plasma membrane 3.2.1

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Transport of carbon dioxide in the blood circulatory system Carbon dioxide is transported in three ways: • 70% is carried in the form of bicarbonate ion (HCO3—) • 23% carbon dioxide combines with haemoglobin to form carbaminohaemoglobin • 7% is dissolved

Brainstorm! Explain why the haemoglobin in foetus has a higher percentage of oxygen saturation compared to haemoglobin in adults.

The transport of carbon dioxide from body cells to tissue capillaries Carbon dioxide (CO2) released by the body cells binds with water (H2O) in the erythrocyte to form carbonic acid (H2CO3).



The carbonic anhydrase enzyme in erythrocyte catalyses this reaction.



Carbonic acid (H2CO3) will break down into bicarbonate ion (HCO3– ) and hydrogen ion (H+).



Then HCO3– diffuses into the blood plasma and is carried to the lungs.

The transport of carbon dioxide from lung capillaries to the alveolus •

When the bicarbonate ion in blood plasma reaches the lung capillaries, it diffuses back into the erythrocyte.



The bicarbonate ion combines again with a hydrogen ion (H+ ) to form carbonic acid (H2CO3).



Carbonic acid ( H2CO3) then breaks down into carbon dioxide and water.



Carbon dioxide diffuses through the lung capillaries into the alveolus and is expelled during exhalation.

Formative Practice

8.3

Brainstorm!

1 What is the value of the partial pressure of oxygen in the atmospheric pressure?

3 Explain how carbon dioxide is transported from the lung capillaries to the alveolus.

2 In what form is carbon dioxide transported in human blood circulatory system?

4 In what form is oxygen carried to the tissues?

8.3.1

Biological Lens Atmospheric pressure at sea level is 760 mm Hg. As the atmosphere consists of 21% oxygen (as per volume), the partial pressure of oxygen is 0.21 x 760 mm Hg or 160 mm Hg. This means that the oxygen pressure in the atmospheric pressure is 160 mm Hg. The partial pressure of carbon dioxide at sea level is 0.23 mm Hg.

Explain why exposure to carbon monoxide for a very short period is more dangerous for an individual as compared to exposure to carbon dioxide.

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Note: Amendments were made to the 3rd point from the top: ….and carried as a carbonic acid (H2CO3). ….. deleted

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CHAPTER 8



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PAGE 36

xylem vessel

VASCULAR TISSUE Vascular tissues are made up of xylem tissue and phloem tissue.

XYLEM TISSUE

PHLOEM TISSUE

The xylem functions in transporting water and mineral salts from the roots to other parts of the plant. Ligneous xylem tissue wall provides support and mechanical strength to the plants.

The phloem functions in transporting organic matters such as sucrose from the leaves to all parts of the plant. sieve tube

Density of certain cell components and specialised cell functions Since the functions performed by cells are different, some cells have a higher density of certain cell components. The density of a cell component in a particular cell is related to the specific function of the cell. Table 2.1 provides examples of cells that have a higher density of certain cell components. TABLE 2.1 Relationship between cell component density with specialised cell functions

Types of cell

Cell component found in abundance

Sperm cell

Muscle cell such as flight muscle cells in insects and birds

Requires a lot of energy to swim towards the uterus and Fallopian tube to fertilise the secondary oocytes Mitochondrion

Plant meristem cell

Chloroplast Spongy mesophyll cell Pancreatic cell

Liver cell

36

Requires a lot of energy to contract and relax to enable movement and flight Requires a lot of energy to carry out active cell division process to produce new cells

Palisade mesophyll cell

Goblet cell in intestinal epithelium and respiratory tract

Function

Rough endoplasmic reticulum Golgi apparatus

Smooth endoplasmic reticulum

Absorbs more sunlight to carry out the process of photosynthesis Increases synthesis and secretion of digestive enzymes Produces mucus



Metabolises carbohydrates



Detoxification of drugs and poisons 2.3.3

Note: Amendment made to Table 2.1 whereby a new row “Smooth endoplasmic reticulum” has been added to the “Liver cell” row.

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Results

Visking tubing

10 ml glucose solution + 10 ml starch suspension

Beaker

400 ml distilled water

Iodine test

Benedict’s test

CHAPTER 3

Contents

Discussion 1 What molecule is found in (a) Visking tubing (b) beaker? 2 What are the inferences that can be made based on the (a) size of the starch molecule (b) size of the glucose molecule compared to the pore size in the Visking tubing? 3 What are the similarities between a Visking tubing and a plasma membrane?

Conclusion Is the hypothesis accepted? Suggest a suitable conclusion.

the movement of substances across a tivitcStudying A 1.2sei3.2 Activity Visking tubing using a simple osmometer

Experiment

Problem statement How do the water molecules permeate across selectively permeable membranes?

Hypothesis Water molecules permeate from an area of high water potential to an area of low water potential.

Variables Manipulated: Time Responding: Increase in the level of sucrose solution in a capillary tube Fixed: Concentration of sucrose solution

Materials 30% sucrose solution, Visking tubing (12 cm), thread and distilled water

Apparatus Retort stand with a clamp, 25 cm capillary tube, syringe, ruler, 500 ml beaker, marker pen, scissors and stopwatch

Procedure 1 Cut a Visking tubing (12 cm). 2 Soak the Visking tubing in water for 5 minutes to soften it. 3 Tie one end of the Visking tubing tightly using thread to form a bag. 4 Fill the Visking tubing with the 30% sucrose solution using the syringe.

3.2.2

Note: Amendment made to Activity 3.2 Apparatus: “50 ml beaker” changed to “500 ml beaker”

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4.1

Water In Form Two, you have learned briefly about water and organic compounds. Examples of organic compounds are carbohydrates, proteins, lipids and nucleic acids. What is the function of organic compounds and water in the cells of an organism?

Properties of water and its importance in a cell POLARITY OF WATER

O H

H

H

O H

hydrogen bond FIGURE 4.1 Hydrogen bond between water molecules

• Water is an inorganic compound consisting of the hydrogen (H) and oxygen (O) elements. • Water molecules are polar molecules because shared electrons between oxygen and hydrogen will be attracted towards oxygen which is more electronegative (δ–). • This polarity produces hydrogen bonds and allows water to act as a universal solvent (Figure 4.1). • The universal solvent properties of water allow solutes such as glucose and electrolytes to be transported through the plasma membranes into cells for biochemical reactions.

COHESIVE FORCE AND ADHESIVE FORCE OF WATER • Water molecules are attached to each other through a cohesive force. • At the same time, water molecules are also attached to other surfaces through adhesive force. • Both forces produce the capillary action which allows water to enter and move along narrow spaces, such as in the xylem tube.

adhesive force cohesive force water

FIGURE 4.2 Cohesive force and adhesive force inside the xylem tube

SPECIFIC HEAT CAPACITY OF WATER

Brainstorm! How do aquatic animals live in frozen sea water?

xylem vessel

PHOTOGRAPH 4.1 A polar bear in the sea covered with ice

• Water has a high specific heat capacity of 4.2 kJ kg-1 °C-1. • This means that 4.2 kJ of heat energy is required to raise the temperature of one kilogram of water by 1°C. • Water absorbs a lot of heat energy with a small rise in temperature. This characteristic is very important to maintain the body temperature of organisms.

Formative Practice

4.1

ICT 4.1

1 What chemical bonds are broken when water changes from liquid to water vapour?

Quiz: Test your understanding of water

2 Why is water known as polar molecule?

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3 State the meaning of adhesive force and cohesive force. 4 Explain how perspiration helps to lower the body temperature.

4.1.1

4.1.2

Note: Amendments made to Figure 4.2 whereby the labels “cohesive force” and “adhesive force” have been interchanged.

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Activity itcA 1.2seitiv5.1

Studying the effect of temperature on the amylase enzyme activity

Experiment

Problem statement What is the effect of temperature on the reaction rate of an amylase enzyme?

Hypothesis An increase in temperature increases the reaction rate of an amylase enzyme up to an optimum temperature. The reaction rate of an enzyme decreases after the optimum temperature.

Variables Manipulated: Temperature Responding: Reaction rate of an amylase enzyme Fixed: The concentration of amylase and starch suspension (substrate) and the pH of the reaction medium

Materials 1% starch suspension, 0.5% amylase enzyme solution, iodine solution, ice and filtered water

Apparatus Beaker, test tube, syringe, dropper, glass rod, white grooved tile, thermometer, Bunsen burner, tripod stand, wire gauze, test tube rack, measuring cylinder and stopwatch

Procedure 1 Using a syringe, put 5 ml of 1% starch suspension into each test tube labelled A1, B1, C1, D1 and E1. 2 Using another syringe, put 2 ml amylase enzyme solution in each test tube labelled A2, B2, C2, D2 and E2. 3 Test tubes A1 and A2, B1 and B2, C1 and C2, D1 and D2, E1 and E2, are placed respectively in 5 separate water baths at fixed temperatures of 20°C, 30°C, 40°C, 50°C and 60°C. 4 Incubate all test tubes for 5 minutes. 5 Meanwhile, prepare a dry, white grooved tile and put a drop of iodine solution into the tile. 6 After incubating for 5 minutes, pour the starch suspension in test tube A1 into test tube A2. Stir the mixture with a glass rod. Start the stopwatch immediately. 7 Use the dropper to extract a drop of the mixture from test tube A2 and drop it immediately into the first groove on the tile containing the iodine solution (The first groove is considered as zero minute). 8 Repeat the iodine test every 30 seconds. Rinse the dropper with the water from the beaker after each sampling. Record the time taken to complete the starch hydrolysis, that is, the time when the mixture remains brownish yellow in colour when tested with the iodine solution.

water bath at respective temperatures

9 Keep all test tubes immersed in the respective water baths throughout the experiment. Repeat steps 5 to 8 for each pair of test tubes B1/B2, C1/C2, D1/D2 and E1/E2. 5 ml starch 2 ml suspension amylase solution

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5.2.9

Note: Amendment made to Procedure No 8: “Repeat the iodine test every 30 minutes” to “Repeat the iodine test every 30 seconds”.

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Enzymes have long been widely used in the commercial sector and for everyday use. The enzymes used are extracted from natural resources such as bacteria or are produced synthetically. Immobilized enzymes are enzymes that combine with inert and insoluble substances to increase the resistance of enzymes towards change in factors such as pH and temperature. With this method, the enzyme molecules will remain in the same position throughout the catalytic reaction and then be separated easily from its product. This technology is known as immobilized enzyme technology. This technology is used in various industrial applications (Photograph 5.1). Formative Practice

5.2

1 How are enzymes produced? 2 How does immobilized enzyme technology help to accelerate the enzyme reaction? 3 Give examples of industries that use enzymes in the manufacturing of products. Digestive enzymes are used in the medical sector Pectinase and cellulase enzymes are used in juice production

Amylase, lipase, protease and cellulase enzymes in bio detergent

Lactase enzymes are used in lactose-free milk

Trypsin enzyme extracts fur from animal hide to make leather products

Protease enzyme separates the fish skin

PHOTOGRAPH 5.1 Enzyme immobilization technology is used in various industrial application 5.3.1

Note: Amendment made to Photograph 5.1 caption: “Lactose enzymes….” changed to “Lactase enzymes…”

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CHAPTER 5

5.3

Application of Enzymes in Daily Life

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equatorial plane centromere

spindle fibres

METAPHASE

• •



Centrioles are at the opposite poles of the cell. The spindle fibres maintain the chromosomes at the equatorial plane. The chromosomes become aligned in a single row on the equatorial plane. Metaphase ends when the centromere begins to divide.

chromosomes

chromosomes

sister chromatids ANAPHASE



TELOPHASE

• • • • • • •

When the chromatids are at the opposite poles, they are now called the daughter chromosome. Each pole contains one set of complete and identical chromosomes. Chromosomes are re-formed as fine chromatin threads. Nucleoli are formed again. Spindle fibres disappear. A new nucleus membrane is formed. The telophase stage is followed by cytokinesis.





The centromere divides into two and the sister chromatids separate. Spindle fibres shorten, contract and the sister chromatids are pulled to the opposite poles of the cell. Anaphase ends when the chromatid arrives at the pole of the cell.

daughter chromosomes

CHAPTER 6



pole of the cells

spindle fibres centriole

nuclear membrane sister chromatids nuclear membrane daughter chromosome FIGURE 6.3 Mitosis 6.2.2

6.2.3

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Note: Amendment is made to the last label at the bottom of the page: “daughter cell” is changed to “daughter chromosome”. Amendment is made to Point 3 of Telophase: “Chromosomes are shaped again…..” changed to “Chromosomes are re-formed…”.

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primary follicle

secondary follicle

secondary oocyte

corpus luteum Graafian follicle secondary oocyte FIGURE 15.6 Oogenesis in the ovaries 3

At birth, a baby girl already has millions of primary oocytes that remain dormant in prophase I meiosis I. The number of oocytes will decrease at puberty.

4

Upon reaching puberty, the primary oocytes will continue meiosis I to form secondary oocyte and a first polar body. Secondary oocyte will begin meiosis II which is then halted at metaphase II. The first polar body will complete meiosis II and form two second polar bodies.

5

A layer of follicular cells envelops the secondary oocyte and is called secondary follicle. The secondary follicle will then develop into the Graafian follicle, which releases oestrogen.

6

A mature Graafian follicle will approach the surface of the ovary and release a secondary oocyte into the Fallopian tube. This process is called ovulation.

7

The secondary oocyte (immature ovum) will complete meiosis II once a sperm penetrates it. Meiosis II produces ovum (n) and a polar body (n). Fertilisation takes place when the sperm nucleus fuses with ovum nucleus and produces a diploid zygote (2n). The rest of the polar bodies will die and will be disintegrated by the ovary.

upon fertilisation

9 Corpus luteum continues to grow and

without fertilisation

10

15.2.2

CHAPTER 15

secretes oestrogen and progesterone. Corpus luteum and secondary oocyte degenerate and dies, and then is removed through menstruation.

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Note: Amendment made to Figure 15.6: The far most right label is changed from “primary oocyte” to “secondary oocyte” Amendment made to No 7 second line: “……and first polar body (n).” changed to “…..and a polar body (n).”